drm/amdgpu: Fix for drm buddy memory corruption

drm/amdgpu: Fix for drm buddy memory corruption

User reported gpu page fault when running graphics applications
and in some cases garbaged graphics are observed as soon as X
starts. This patch fixes all the issues.

Fixed the typecast issue for fpfn and lpfn variables, thus
preventing the overflow problem which resolves the memory
corruption.

Signed-off-by: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@amd.com>
Reported-by: Mike Lothian <mike@fireburn.co.uk>
Tested-by: Mike Lothian <mike@fireburn.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20220714101214.7620-1-Arunpravin.PaneerSelvam@amd.com
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Christian König <christian.koenig@amd.com>