Puts the i2c adapter in common place for sharing by RAS
and upcoming data read from FRU EEPROM feature.

v2:
Move i2c adapter to amdgpu_pm and rename it.

v3: Move i2c adapter init to ASIC specific code and get rid
of the switch case in amdgpu_device
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>