ixgbe: add X550 support for external PHY and forced 1G/10G support

ixgbe: add X550 support for external PHY and forced 1G/10G support

This patch adds x550 external PHY interrupt and forced 1G/10G support.
This included enabling and handling LSC and thermal sensor interrupt.
ixgbe_handle_lasi() has been added for handling the interrupts received
over SDP0 from the external 10baseT PHY. ixgbe_enable_lasi_ext_t_x550em
and ixgbe_get_lasi_ext_t_x550em have been added to X550em to enable
mask and check interrupt flags for the external PHY.

Forced 1G/10G link speed is handled via ixgbe_mac_link_t_X550em.
ixgbe_seupt_mac_link_t_X550em sets up the internal PHY and external PHY
to either iXFI (10G) or KX (1G) based on the user selected auto
advertised link speed setting. Then sets up the external PHY auto
advertised link speed.

Signed-off-by: Don Skidmore <donald.c.skidmore@intel.com>
Tested-by: Krishneil Singh <krishneil.k.singh@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>