amdkfd: Display MEC fw version in topology node

This patch displays the firmware version of the microcode that is currently
running in the MEC.
This is needed for the HSA RT, so it could differentiate its behavior based on
fw version. e.g. workarounds for bugs in fw

v2: Send the KGD_ENGINE_MEC1 as a parameter to the get_fw_version()

Signed-off-by: Oded Gabbay <oded.gabbay@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>