avutil/arm: fix armv5 build

https://code.ffmpeg.org/FFmpeg/FFmpeg/commit/471db1d323aaed50ff922f0da76ecc8e45c4e817

added armv6 optimizations and guarded the include with

  #elif ARCH_ARM && HAVE_ARMV6

but guarded the code only with

  #elif ARCH_ARM

causing a build error with armv5 toolchains:

libavutil/pixelutils.c: In function ‘av_pixelutils_get_sad_fn’:
libavutil/pixelutils.c:102:5: error: implicit declaration of function
 ‘ff_pixelutils_sad_init_arm’ [-Wimplicit-function-declaration]

Signed-off-by: Bernd Kuhls <bernd@kuhls.net>

libavutil/pixelutils.c

@@ -30,7 +30,7 @@
 
 #if ARCH_AARCH64 && HAVE_NEON
 #include "aarch64/pixelutils.h"
-#elif ARCH_ARM && HAVE_ARMV6
+#elif ARCH_ARM
 #include "arm/pixelutils.h"
 #elif ARCH_MIPS && HAVE_MSA
 #include "mips/pixelutils.h"