eth: fbnic: Add hardware monitoring support via HWMON interface

eth: fbnic: Add hardware monitoring support via HWMON interface

This patch adds support for hardware monitoring to the fbnic driver,
allowing for temperature and voltage sensor data to be exposed to
userspace via the HWMON interface. The driver registers a HWMON device
and provides callbacks for reading sensor data, enabling system
admins to monitor the health and operating conditions of fbnic.

Signed-off-by: Sanman Pradhan <sanmanpradhan@meta.com>
Reviewed-by: Kalesh AP <kalesh-anakkur.purayil@broadcom.com>
Link: https://patch.msgid.link/20241014152709.2123811-1-sanman.p211993@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>