[sfputil] Configure the debug loopback mode only on the relevant lanes of the logical port

[xinyulin]

What I did

This update enhances the loopback command functionality to support configuring the loopback mode for specific logical ports, instead of applying the configuration to the entire physical port.

How I did it

By calculating the lane mask according to the port's configuration and state data, the loopback mode can now be accurately set for the specified port, ensuring that other unrelated logical ports are not affected during diagnostic operations.

How to verify it

Tested under Cisco8111 with Credo C1 cable.

The sfputil debug loopback command will now only affect the relevant lanes of the logical port.

Set host input loopback mode on logical port Ethernet80, the expected value of page 0x13, byte 0xB7= 0x0F

Set media input loopback mode on logical port Ethernet84, the expected value of page 0x13, byte 0xB5= 0xF0

Previous command output (if the output of a command-line utility has changed)

New command output (if the output of a command-line utility has changed)