drm/exec, drm/gpuvm: Prefer u32 over uint32_t

The relatively recently introduced drm/exec utility was using uint32_t
in its interface, which was then also carried over to drm/gpuvm.

Prefer u32 in new code and update drm/exec and drm/gpuvm accordingly.

Cc: Christian König <christian.koenig@amd.com>
Cc: Danilo Krummrich <dakr@redhat.com>
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Danilo Krummrich <dakr@redhat.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240119090557.6360-1-thomas.hellstrom@linux.intel.com