drm/amdkfd: change error to warning message for SDMA queues creation

SDMA doesn't support oversubsciption, it is the user matter to create
queues over HW limit, but not supposed to be a KFD error.

Signed-off-by: Eric Huang <jinhuieric.huang@amd.com>
Reviewed-by: Harish Kasiviswanathan <Harish.Kasiviswanathan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>