sparc: io: remove duplicate relaxed accessors on sparc32

Commit 1191ccb3 ("sparc: io: implement dummy relaxed accessor
macros for writes") added the relaxed accessors (readl_relaxed etc) in
a file that is shared between sparc32 and sparc64. However, the earlier
e1039fb4

 ("sparc32: introduce asm-generic/io.h") had already changed
the sparc32 implementation to use asm-generic/io.h, which provides the
same macros, resulting in lots of build errors.

This moves the definitions from the shared sparc file into the
sparc64-only file to fix the sparc32 build regression.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Fixes: 1191ccb3 ("sparc: io: implement dummy relaxed accessor macros for writes")