Display error counters via debugfs node.

Link: https://lore.kernel.org/r/20210111093134.1206-3-njavali@marvell.comReviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: Saurav Kashyap <skashyap@marvell.com>
Signed-off-by: Nilesh Javali <njavali@marvell.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>