staging: rtl8712: code style fix

Fixed the warnings from checkpatch.pl on file rtl8712/mlme_linux.c
Avoided multiple line dereferences in the code

Signed-off-by: Tejaswini Poluri <tejaswinipoluri3@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>