x86: h264qpel: Only define mmxext QPEL functions if H264QPEL is enabled

This fixes compilation with --disable-everything and components enabled.

libavcodec/x86/h264_qpel.c

@@ -1286,6 +1286,6 @@ QPEL16_OP(mc31, MMX)\
 QPEL16_OP(mc32, MMX)\
 QPEL16_OP(mc33, MMX)
 
-#if ARCH_X86_32 && HAVE_YASM // ARCH_X86_64 implies sse2+
+#if ARCH_X86_32 && HAVE_YASM && CONFIG_H264QPEL // ARCH_X86_64 implies SSE2+
 QPEL16(mmxext)
 #endif