net/mlx5: Refactor PTP clock devcom pairing

net/mlx5: Refactor PTP clock devcom pairing

Refactor PTP clock device component pairing to use the clock identity
buffer instead of casting it to a u64 key. This change leverages the new
software system image GUID infrastructure.

Changes include:
- Pass identity buffer to mlx5_shared_clock_register().
- Use memcpy for identity buffer in devcom matching attributes.
- Remove intermediate u64 key conversion.
- Add BUILD_BUG_ON to ensure identity size fits in match key.

Signed-off-by: Mark Bloch <mbloch@nvidia.com>
Reviewed-by: Shay Drori <shayd@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://patch.msgid.link/1761211020-925651-4-git-send-email-tariqt@nvidia.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>