staging: rtl8712: fix coding style error reported from checkpatch

removed the following:
ERROR: code indent should use tabs where possible
WARNING: please, no spaces at the start of a line
WARNING: Statements should start on a tabstop

Signed-off-by: Omri Arad <omriarad3@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>