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>