bnxt_en: read the clause type from the PHY ID

Currently driver hard code Clause 45 based on speed supported by the
PHY. Instead read the clause type from the PHY ID provided as input
to the mdio ioctl.

Fixes: 0ca12be9 ("bnxt_en: Add support for mdio read/write to external PHY")
Signed-off-by: Vasundhara Volam <vasundhara-v.volam@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>