scsi: lpfc: Fix Max Frame Size value shown in fdmishow output

Max Frame Size value is shown as 34816 in fdmishow from Switch.

The driver uses bbRcvSize in common service param which is obtained from
the READ_SPARM mailbox command. The bbRcvSize field which is displayed is a
three nibble field but the driver is printing a full four nibbles.

Fix by masking off the upper nibble.

Signed-off-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: James Smart <jsmart2021@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>