staging: rtl8712: remove assignment of 0 to a static global variable

fixes the following checkpatch warning:

drivers/staging/rtl8712/os_intfs.c:99: ERROR: do not initialise statics
to 0 or NULL

as statics are always initialised to 0.

Signed-off-by: Devendra Naga <devendra.aaru@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>