Staging: w35und: remove atomic op wrappers

Use the kernel provided atomic op functions and remove the OS_ATOMIC and
related wrapper macros.

Acked-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>