The return value of platform_device_register_simple() should be checked by
IS_ERR().

This patch also fix misc_register() error case.  Because misc_register()
returns error code.

Cc: Sebastien Bouchard <sebastien.bouchard@ca.kontron.com>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>