drm/i915/display: handle systems with duplicate psf gv points

There could be multiple qgv and psf gv points with similar values.
Apparently pcode's handling of psf and qgv points are different. For
qgv case, pcode sets whatever is asked by the driver. But in case
of psf gv points, it compares the bw from points before setting the
mask. This can cause problems in scenarios where we have to disable
sagv by setting the highest bw point and there could be multiple
points with highest bw. So to set the maximum psf gv point, find
out all the points with the highest bw and set all together.

v1: - use the same treatment to qgv points as well (Vinod)

v2: - pcode confirms that for qgv points, it sets whatever the
driver sets (Vinod)

Reviewed-by: Jouni Högander <[e-mail]>
Signed-off-by: Stanislav Lisovskiy <[e-mail]>
Signed-off-by: Vinod Govindapillai <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/i915/display/intel_bw.c

···
 		if (max_data_rate > max_bw) {
 			max_bw_point_mask = BIT(i);
 			max_bw = max_data_rate;
+		} else if (max_data_rate == max_bw) {
+			max_bw_point_mask |= BIT(i);
 		}
 	}