scsi: ufs: qcom: Remove unnecessary mb() after writing testbus config

Currently, the testbus configuration is written and completed with an mb().

mb() ensures that the write completes, but completion doesn't mean that it
isn't stored in a buffer somewhere. The recommendation for ensuring this
bit has taken effect on the device is to perform a read back to force it to
make it all the way to the device. This is documented in device-io.rst and
a talk by Will Deacon on this can be seen over here:

    https://youtu.be/i6DayghhA8Q?si=MiyxB5cKJXSaoc01&t=1678

But, there's really no reason to even ensure completion before
continuing. The only requirement here is that this write is ordered to this
endpoint (which readl()/writel() guarantees already). For that reason the
mb() can be dropped altogether without anything forcing completion.

Fixes: 9c46b8676271 ("scsi: ufs-qcom: dump additional testbus registers")
Signed-off-by: Andrew Halaney <ahalaney@redhat.com>
Link: https://lore.kernel.org/r/20240329-ufs-reset-ensure-effect-before-delay-v5-3-181252004586@redhat.com
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/ufs/host/ufs-qcom.c

@@ -1443,11 +1443,6 @@ int ufs_qcom_testbus_config(struct ufs_qcom_host *host)
 		    (u32)host->testbus.select_minor << offset,
 		    reg);
 	ufs_qcom_enable_test_bus(host);
-	/*
-	 * Make sure the test bus configuration is
-	 * committed before returning.
-	 */
-	mb();
 
 	return 0;
 }