staging: wlan-ng: Fix dereference before NULL check

Smatch is warning about a dereference before we check for NULL.
This patch moves the dereference to after the NULL check.

Smatch warning:
drivers/staging/wlan-ng/cfg80211.c:345 prism2_scan() warn:
	variable dereferenced before check 'request' (see line 332)

Signed-off-by: Emil Goode <emilgoode@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>