videodsp_armv5te: remove #if HAVE_ARMV5TE_EXTERNAL

libavutil/arm/asm.S sets '.arch' depending on HAVE_ARMV5TE so that
assembling armv5te code will always succeed even if the default -march
flag does not support it. HAVE_ARMV5TE_EXTERNAL tests assembling code
with the default arch.
Fixes the missing symbol ff_prefetch_arm with --cpu= not including
armv5te.

CC: libav-stable@libav.org

libavcodec/arm/videodsp_armv5te.S

@@ -22,7 +22,6 @@
 #include "config.h"
 #include "libavutil/arm/asm.S"
 
-#if HAVE_ARMV5TE_EXTERNAL
 function ff_prefetch_arm, export=1
         subs            r2,  r2,  #1
         pld             [r0]
@@ -30,4 +29,3 @@ function ff_prefetch_arm, export=1
         bne             ff_prefetch_arm
         bx              lr
 endfunc
-#endif