macintosh/windfarm_pm91: Fix warning comparing pointer to 0

Avoid pointer type value compared with 0 to make code clear.

Signed-off-by: Haowen Bai <[e-mail]>
Signed-off-by: Michael Ellerman <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/macintosh/windfarm_pm91.c

···
 
 	/* First, locate the PID params in SMU SBD */
 	hdr = smu_get_sdb_partition(SMU_SDB_CPUPIDDATA_ID, NULL);
-	if (hdr == 0) {
+	if (!hdr) {
 		printk(KERN_WARNING "windfarm: CPU PID fan config not found "
 		       "max fan speed\n");
 		goto fail;