scsi: mpt3sas: Fix error returns in BRM_status_show

BRM_status_show() has several error branches, but none of them record the
error in the error return.

Also while at it remove the manual mutex_unlock() of the pci_access_mutex
in case of an ongoing pci error recovery or host removal and jump to the
cleanup label instead.

Note: We can safely jump to out from here as io_unit_pg3 is initialized to
NULL and if it hasn't been allocated, kfree() skips the NULL pointer.

[mkp: compilation warning]

Link: https://lore.kernel.org/r/20200701131454.5255-1-johannes.thumshirn@wdc.comReviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Acked-by: Sreekanth Reddy <sreekanth.reddy@broadcom.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/mpt3sas/mpt3sas_ctl.c

@@ -3149,15 +3149,14 @@ BRM_status_show(struct device *cdev, struct device_attribute *attr,
 	}
 	/* pci_access_mutex lock acquired by sysfs show path */
 	mutex_lock(&ioc->pci_access_mutex);
-	if (ioc->pci_error_recovery || ioc->remove_host) {
-		mutex_unlock(&ioc->pci_access_mutex);
-		return 0;
-	}
+	if (ioc->pci_error_recovery || ioc->remove_host)
+		goto out;
 
 	/* allocate upto GPIOVal 36 entries */
 	sz = offsetof(Mpi2IOUnitPage3_t, GPIOVal) + (sizeof(u16) * 36);
 	io_unit_pg3 = kzalloc(sz, GFP_KERNEL);
 	if (!io_unit_pg3) {
+		rc = -ENOMEM;
 		ioc_err(ioc, "%s: failed allocating memory for iounit_pg3: (%d) bytes\n",
 			__func__, sz);
 		goto out;
@@ -3167,6 +3166,7 @@ BRM_status_show(struct device *cdev, struct device_attribute *attr,
 	    0) {
 		ioc_err(ioc, "%s: failed reading iounit_pg3\n",
 			__func__);
+		rc = -EINVAL;
 		goto out;
 	}
 
@@ -3174,12 +3174,14 @@ BRM_status_show(struct device *cdev, struct device_attribute *attr,
 	if (ioc_status != MPI2_IOCSTATUS_SUCCESS) {
 		ioc_err(ioc, "%s: iounit_pg3 failed with ioc_status(0x%04x)\n",
 			__func__, ioc_status);
+		rc = -EINVAL;
 		goto out;
 	}
 
 	if (io_unit_pg3->GPIOCount < 25) {
 		ioc_err(ioc, "%s: iounit_pg3->GPIOCount less than 25 entries, detected (%d) entries\n",
 			__func__, io_unit_pg3->GPIOCount);
+		rc = -EINVAL;
 		goto out;
 	}