staging: rtl8723bs: Rewrite comparison to NULL

Rewrite comparison to NULL by modifying (p != NULL) to (p).
Issue reported by checkpatch.

Signed-off-by: Izabela Bakollari <izabela.bakollari@gmail.com>
Link: https://lore.kernel.org/r/20201026232310.48128-1-izabela.bakollari@gmail.com


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