NTB: switchtec_ntb: fix spelling mistake: "peforming" -> "performing"

Trivial fix to spelling mistake in dev_err error message
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-By: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>

drivers/ntb/hw/mscc/ntb_hw_switchtec.c

@@ -172,7 +172,7 @@ static int switchtec_ntb_part_op(struct switchtec_ntb *sndev,
 
 	if (ps == status) {
 		dev_err(&sndev->stdev->dev,
-			"Timed out while peforming %s (%d). (%08x)",
+			"Timed out while performing %s (%d). (%08x)",
 			op_text[op], op,
 			ioread32(&ctl->partition_status));