drm/amdgpu: introduce a firmware debugfs to dump all current firmware versions

This patch implements the debugfs to dump all currect firmware
version:

root@jenkins-All-Series:/home/jenkins# cat /sys/kernel/debug/dri/0/amdgpu_firmware_info
VCE feature version: 0, firmware version: 0x34040300
UVD feature version: 0, firmware version: 0x01451000
MC feature version: 0, firmware version: 0x00000000
ME feature version: 37, firmware version: 0x00000093
PFP feature version: 37, firmware version: 0x000000da
CE feature version: 37, firmware version: 0x00000080
RLC feature version: 1, firmware version: 0x0000010e
MEC feature version: 37, firmware version: 0x0000029e
MEC2 feature version: 37, firmware version: 0x0000029e
SMC feature version: 0, firmware version: 0x013353e6
SDMA0 feature version: 31, firmware version: 0x00000036
SDMA1 feature version: 0, firmware version: 0x00000036

Suggested-by: Alex Deucher <Alexander.Deucher@amd.com>
Signed-off-by: Huang Rui <ray.huang@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>