staging: rtl8712: add spaces around operators

Add spaces around operators to adhere to Linux kernel coding style.
Reported by checkpatch.

Signed-off-by: Zhansaya Bagdauletkyzy <zhansayabagdaulet@gmail.com>
Link: https://lore.kernel.org/r/1fa63e851a6fa403798b95b64d9147c9b3b02c93.1617697237.git.zhansayabagdaulet@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>