drm/xe/xe_migrate: Cast to output precision before multiplying operands

Addressing potential overflow in result of  multiplication of two lower
precision (u32) operands before widening it to higher precision
(u64).

-v2
Fix commit message and description. (Rodrigo)

Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240401175300.3823653-1-himal.prasad.ghimiray@intel.com
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
(cherry picked from commit 34820967

)
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>