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

This reverts commit c8c7736c10.

libswscale/arm/Makefile

@@ -1,4 +1,4 @@
-# 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);
 
 }