build: replace use of HAVE_SDL2 with existing CONFIG_SDL2

There is no need for duplication.

configure

@@ -2068,7 +2068,6 @@ HAVE_LIST="
     MMAL_PARAMETER_VIDEO_MAX_NUM_CALLBACKS
     perl
     pod2man
-    sdl2
     section_data_rel_ro
     sndio
     texi2html

libavdevice/opengl_enc.c

@@ -46,7 +46,7 @@
 #include <GL/glx.h>
 #endif
 
-#if HAVE_SDL2
+#if CONFIG_SDL2
 #include <SDL.h>
 #endif
 
@@ -174,7 +174,7 @@ static const GLushort g_index[6] =
 typedef struct OpenGLContext {
     AVClass *class;                    ///< class for private options
 
-#if HAVE_SDL2
+#if CONFIG_SDL2
     SDL_Window *window;
     SDL_GLContext glcontext;
 #endif
@@ -343,7 +343,7 @@ static int opengl_control_message(AVFormatContext *h, int type, void *data, size
     return AVERROR(ENOSYS);
 }
 
-#if HAVE_SDL2
+#if CONFIG_SDL2
 static int opengl_sdl_process_events(AVFormatContext *h)
 {
     OpenGLContext *opengl = h->priv_data;
@@ -448,14 +448,14 @@ static int av_cold opengl_sdl_load_procedures(OpenGLContext *opengl)
 
 #undef LOAD_OPENGL_FUN
 }
-#endif /* HAVE_SDL2 */
+#endif /* CONFIG_SDL2 */
 
 #if defined(__APPLE__)
 static int av_cold opengl_load_procedures(OpenGLContext *opengl)
 {
     FFOpenGLFunctions *procs = &opengl->glprocs;
 
-#if HAVE_SDL2
+#if CONFIG_SDL2
     if (!opengl->no_window)
         return opengl_sdl_load_procedures(opengl);
 #endif
@@ -505,7 +505,7 @@ static int av_cold opengl_load_procedures(OpenGLContext *opengl)
         return AVERROR(ENOSYS); \
     }
 
-#if HAVE_SDL2
+#if CONFIG_SDL2
     if (!opengl->no_window)
         return opengl_sdl_load_procedures(opengl);
 #endif
@@ -931,7 +931,7 @@ static int opengl_create_window(AVFormatContext *h)
     int ret;
 
     if (!opengl->no_window) {
-#if HAVE_SDL2
+#if CONFIG_SDL2
         if ((ret = opengl_sdl_create_window(h)) < 0) {
             av_log(opengl, AV_LOG_ERROR, "Cannot create default SDL window.\n");
             return ret;
@@ -963,7 +963,7 @@ static int opengl_release_window(AVFormatContext *h)
     int ret;
     OpenGLContext *opengl = h->priv_data;
     if (!opengl->no_window) {
-#if HAVE_SDL2
+#if CONFIG_SDL2
         SDL_GL_DeleteContext(opengl->glcontext);
         SDL_DestroyWindow(opengl->window);
         SDL_Quit();
@@ -1099,7 +1099,7 @@ static av_cold int opengl_write_header(AVFormatContext *h)
 
     glClear(GL_COLOR_BUFFER_BIT);
 
-#if HAVE_SDL2
+#if CONFIG_SDL2
     if (!opengl->no_window)
         SDL_GL_SwapWindow(opengl->window);
 #endif
@@ -1194,7 +1194,7 @@ static int opengl_draw(AVFormatContext *h, void *input, int repaint, int is_pkt)
     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(pix_fmt);
     int ret;
 
-#if HAVE_SDL2
+#if CONFIG_SDL2
     if (!opengl->no_window && (ret = opengl_sdl_process_events(h)) < 0)
         goto fail;
 #endif
@@ -1235,7 +1235,7 @@ static int opengl_draw(AVFormatContext *h, void *input, int repaint, int is_pkt)
     ret = AVERROR_EXTERNAL;
     OPENGL_ERROR_CHECK(opengl);
 
-#if HAVE_SDL2
+#if CONFIG_SDL2
     if (!opengl->no_window)
         SDL_GL_SwapWindow(opengl->window);
 #endif