staging: rtl8723bs: put constant on the right side of a test in os_dep/ioctl_cfg80211.c

fix following post-commit hook checkpatch issue:

CHECK: Comparison to NULL could be written "psta"
72: FILE: drivers/staging/rtl8723bs/os_dep/ioctl_cfg80211.c:854:
+			if (psta != NULL) {

Signed-off-by: Fabio Aiuto <fabioaiuto83@gmail.com>
Link: https://lore.kernel.org/r/5ac547f3a4bd228f372da7057bbfb3cac1535857.1618064274.git.fabioaiuto83@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>