staging: rtl8712: remove unnecessary braces in while loop

Fixed a linux coding style.

Reported by checkpath:

WARNING: braces {} are not necessary for single statement blocks

Signed-off-by: Hoorad Farrokh <hourrad.f@gmail.com>
Link: https://lore.kernel.org/r/4vmxiuz5u2f2vehngdccj5q7bakpujagk72ty5ounfv2nfzxgr@lqkdn5fecc23
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>