staging: rtl8723bs: simplify NULL pointer comparisons in rtw_recv.h

staging: rtl8723bs: simplify NULL pointer comparisons in rtw_recv.h

Fix checkpatch.pl warnings regarding explicit comparisons to NULL.
The kernel coding style prefers the shorter if (!ptr) idiom over
if (ptr == NULL). Clean up the inline functions in rtw_recv.h to
match this standard.

Signed-off-by: Abhai Kollara <abhai@protonmail.com>
Reviewed-by: Luka Gejak <luka.gejak@linux.dev>
Link: https://patch.msgid.link/20260430201158.2807823-1-abhai@protonmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>