drm/radeon: Stop changing the drm_driver struct

With only the kms driver left, we can fold this in. This means
we need to move the ioctl table, which means one additional ioctl
must be defined in headers.

Also there's a conflict between the radeon_init macro and the module
init function, so rename the module functions to avoid that.

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: amd-gfx@lists.freedesktop.org
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20201104100425.1922351-1-daniel.vetter@ffwll.ch