drm/amd/powerplay: Add interface to lock SMU HW I2C.

v2:
PPSMC_MSG_RequestI2CBus seems not to work and so to avoid conflict
over I2C bus and engine disable thermal control access to
force SMU stop using the I2C bus until the issue is reslolved.

Expose and call vega20_is_smc_ram_running to skip locking when SMU
FW is not yet loaded.

v3:
Remove the prevoius hack as the SMU found the bug.

v5: Typo fix

Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>