net/mlx5: Add register layout to support extended link state

Add needed structure layouts and defines for pddr register
(Port Diagnostics Database Register) and the troublshooting page.

This will be used to get extended link state from the monitor opcode
bits.

Signed-off-by: Moshe Tal <moshet@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>