swscale: disable ARM code until its build failure with clang/iphone is fixed

See: "19:40 Yu Xiaolei Re: [FFmpeg-devel] [PATCH] fix build with gas-preprocessor.pl"
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libswscale/arm/Makefile

-OBJS        += arm/swscale_unscaled.o
+# OBJS        += arm/swscale_unscaled.o
 
-NEON-OBJS   += arm/rgb2yuv_neon_32.o
-NEON-OBJS   += arm/rgb2yuv_neon_16.o
+# NEON-OBJS   += arm/rgb2yuv_neon_32.o
+# NEON-OBJS   += arm/rgb2yuv_neon_16.o

libswscale/swscale_unscaled.c

@@ -1582,8 +1582,8 @@ void ff_get_unscaled_swscale(SwsContext *c)
         ff_get_unscaled_swscale_bfin(c);
     if (ARCH_PPC)
         ff_get_unscaled_swscale_ppc(c);
-    if (ARCH_ARM)
-        ff_get_unscaled_swscale_arm(c);
+//     if (ARCH_ARM)
+//         ff_get_unscaled_swscale_arm(c);
 
 }