staging: rtl8712: Add spaces around <<

Fix checkpatch error "CHECK: spaces preferred around that '<<'".

Signed-off-by: Marco Villegas <git@marvil07.net>
Link: https://lore.kernel.org/r/20190802194737.12252-1-git@marvil07.net


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