staging: rtl8712: remove trailing whitespace

Fix the following checkpatch.pl error:

ERROR: trailing whitespace
Signed-off-by: Felix Yan <felixonmars@archlinux.org>
Link: https://lore.kernel.org/r/20240730063746.176245-1-felixonmars@archlinux.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>