drm/amd/display: Separate setting and programming of cursor

We're seeing issues when user-space tries to do an atomic update of
the primary surface, as well as the cursor. These two updates are
separate calls into DC and don't currently act as an atomic update.
This might lead to cursor updates being locked out and cursors
stuttering.

In order to solve this problem we want to separate the setting
and programming of cursor attributes and position. That's what
we're doing in this patch. The subsequent patch will then be
able to use the cursor setters in independent cursor updates,
as well as in atomic commits.

Reviewed-by: Agustin Gutierrez <agustin.gutierrez@amd.com>
Acked-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>