drm/amd/display: Fix unnecessary cast warnings from checkpatch

[ Upstream commit c299cb6e ]

This patch addresses warnings produced by the checkpatch script
related to unnecessary casts that could potentially hide bugs.

The specific warnings are as follows:
- Warning at drivers/gpu/drm/amd/display/dc/dml2/dml21/dml21_wrapper.c:16
- Warning at drivers/gpu/drm/amd/display/dc/dml2/dml21/dml21_wrapper.c:20
- Warning at drivers/gpu/drm/amd/display/dc/dml2/dml21/dml21_wrapper.c:30

Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Rohit Chavan <roheetchavan@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Stable-dep-of: cd9e6d6f ("drm/amd/display/dml2: use vzalloc rather than kzalloc")
Signed-off-by: Sasha Levin <sashal@kernel.org>