staging: rtl8712: remove space after cast

Remove the unnecessary space immediately after a cast. Identified by
checkpatch: CHECK: No space is necessary after a cast.

Signed-off-by: Deborah Brouwer <deborahbrouwer3563@gmail.com>
Link: https://lore.kernel.org/r/b1ba94644f5204505623ffc64614671aac30bbd8.1617674639.git.deborahbrouwer3563@gmail.com


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