arm: introduce asm/swab.h

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/arm/include/asm/Kbuild b/arch/arm/include/asm/Kbuild
index 73237bd..43b0b2b 100644
--- a/arch/arm/include/asm/Kbuild
+++ b/arch/arm/include/asm/Kbuild
@@ -1,3 +1,4 @@
 include include/asm-generic/Kbuild.asm
 
 unifdef-y += hwcap.h
+unifdef-y += swab.h