drm/amd/display/dm: drop hw_support check in amdgpu_dm_i2c_xfer()

[ Upstream commit 33da70bd ]

DC supports SW i2c as well.  Drop the check.

Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>