avcodec/x86/hpeldsp_rnd_template: silence -Wunused-function on --disable-mmx

This silences some of the -Wunused-function warnings when compiled with --disable-mmx, e.g
http://fate.ffmpeg.org/log.cgi?time=20150919094617&log=compile&slot=x86_64-archlinux-gcc-disable-mmx.
Header guards are too brittle and ugly for this case.
Signed-off-by: Ganesh Ajjanagadde <gajjanagadde@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/x86/hpeldsp_rnd_template.c

@@ -28,7 +28,7 @@
 #include <stdint.h>
 
 // put_pixels
-static void DEF(put, pixels8_x2)(uint8_t *block, const uint8_t *pixels, ptrdiff_t line_size, int h)
+av_unused static void DEF(put, pixels8_x2)(uint8_t *block, const uint8_t *pixels, ptrdiff_t line_size, int h)
 {
     MOVQ_BFE(mm6);
     __asm__ volatile(
@@ -60,7 +60,7 @@ static void DEF(put, pixels8_x2)(uint8_t *block, const uint8_t *pixels, ptrdiff_
         :REG_a, "memory");
 }
 
-static void DEF(put, pixels16_x2)(uint8_t *block, const uint8_t *pixels, ptrdiff_t line_size, int h)
+av_unused static void DEF(put, pixels16_x2)(uint8_t *block, const uint8_t *pixels, ptrdiff_t line_size, int h)
 {
     MOVQ_BFE(mm6);
     __asm__ volatile(
@@ -135,7 +135,7 @@ static void DEF(put, pixels8_y2)(uint8_t *block, const uint8_t *pixels, ptrdiff_
         :REG_a, "memory");
 }
 
-static void DEF(avg, pixels16_x2)(uint8_t *block, const uint8_t *pixels, ptrdiff_t line_size, int h)
+av_unused static void DEF(avg, pixels16_x2)(uint8_t *block, const uint8_t *pixels, ptrdiff_t line_size, int h)
 {
     MOVQ_BFE(mm6);
         __asm__ volatile(