ndk: Replace 'asm' with '__asm__' in <asm/byteorder.h>

See https://review.source.android.com/#change,20076 for details.
Essentially this is to allow compilation with -std=c99

Change-Id: I4c830c38b2615352765ee40773c5aa701e5d2b68
diff --git a/ndk/platforms/android-3/arch-arm/include/asm/byteorder.h b/ndk/platforms/android-3/arch-arm/include/asm/byteorder.h
index 4da37bf..b869695 100644
--- a/ndk/platforms/android-3/arch-arm/include/asm/byteorder.h
+++ b/ndk/platforms/android-3/arch-arm/include/asm/byteorder.h
@@ -22,7 +22,7 @@
 #ifndef __thumb__
  if (!__builtin_constant_p(x)) {
 
- asm ("eor\t%0, %1, %1, ror #16" : "=r" (t) : "r" (x));
+ __asm__ ("eor\t%0, %1, %1, ror #16" : "=r" (t) : "r" (x));
  } else
 #endif
  t = x ^ ((x << 16) | (x >> 16));