drm/i915/vdsc: Fix first_line_bpg_offset calculation

On checking DSC1.1 Errata and DSC 1.2 spec the current formula
we were using was incorrect to calculate first_line_bpg_offset.
The new fixed formula is derived from C model.

--v2
-Use clamp function in linux/minmax.h [Ankit]

--v3
-remove linux/minmax.h header

Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230804083737.3844575-1-suraj.kandpal@intel.com