sparc32: nocheck uaccess coding style tweaks

Sam Ravnborg suggested packing single-lines cases in switch statements
in nocheck uaccess macros makes for easier to read code.

Suggested-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>