drm/amd/display: Use NULL pointer instead of plain integer

Assigning 0L to a pointer variable caused the following warning:

drivers/gpu/drm/amd/amdgpu/../display/dc/dml/dsc/rc_calc_fpu.c:71:40:
warning: Using plain integer as NULL pointer

In order to remove this warning, this commit assigns a NULL pointer to
the pointer variable that caused this issue.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Magali Lemes <magalilemes00@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drm/amd/display: Fix warning comparing pointer to 0

Fix the following coccicheck warning:

./drivers/gpu/drm/amd/display/dc/dml/dsc/rc_calc_fpu.c:96:14-15: WARNING
comparing pointer to 0.

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drm/amd/display: fixed an error related to 4:2:0/4:2:2 DSC

[Why]
OPTC_BYTES_PER_PIXEL calculation for 4:2:2 and 4:2:0 could have error.

[How]
Change to use following formula:
OPTC_DSC_BYTES_PER_PIXEL = ceiling((chunk size * 2^28) / slice width)

v2: squash in 64 bit divide fix (Alex)

Reviewed-by: Wenjing Liu <Wenjing.Liu@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Bing Guo <Bing.Guo@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drm/amd/display: move FPU associated DSC code to DML folder

[Why & How]
As part of the FPU isolation work documented in
https://patchwork.freedesktop.org/series/93042/, isolate code that uses
FPU in DSC to DML, where all FPU code should locate.

This change does not refactor any functions but move code around.

Cc: Christian König <christian.koenig@amd.com>
Cc: Hersen Wu <hersenxs.wu@amd.com>
Cc: Anson Jacob <Anson.Jacob@amd.com>
Cc: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Acked-by: Agustin Gutierrez <agustin.gutierrez@amd.com>
Tested-by: Anson Jacob <Anson.Jacob@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>