staging: rtl8712: style fix over 80 characters warnings

This patch fixes various coding style issues in the rtl8712 module as
noted by checkpatch.pl by reducing the characters per line to under
80.

It fixes the following checkpatch.pl warning:

WARNING: line over 80 characters

Signed-off-by: Martin Homuth <martin@martinhomuth.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>