Revert "Use inline keyword without underscores consistently"

This reverts commit 58f06e11122723d68c5cb393aeb4ed1c7a2e7bfe.

Bare `inline` is not ANSI C compatible, and NDK users may be using
that.

Test: treehugger
Change-Id: I82c5424522142001cd59da63ef3fd440014451ad
diff --git a/libc/include/bits/swab.h b/libc/include/bits/swab.h
index ebb7c74..9591c2e 100644
--- a/libc/include/bits/swab.h
+++ b/libc/include/bits/swab.h
@@ -33,7 +33,7 @@
 #include <sys/types.h>
 
 #if !defined(__BIONIC_SWAB_INLINE)
-#define __BIONIC_SWAB_INLINE static inline
+#define __BIONIC_SWAB_INLINE static __inline
 #endif
 
 __BEGIN_DECLS