sh: Proper __put_user_asm() size mismatch fix.

This fixes up the workaround in 2b4b2bb4
and cleans up __put_user_asm() to get the sizing right from the onset.

Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>