drm/i915/selftests: fixup min_alignment usage

Trying to cast the region id into the region type doesn't work too well,
since the i915_vm_min_alignment() won't give us the correct value for
the stolen-lmem case.
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Nirmoy Das <nirmoy.das@linux.intel.com>
Cc: Ramalingam C <ramalingam.c@intel.com>
Reviewed-by: Nirmoy Das <nirmoy.das@linux.intel.com>
Reviewed-by: Ramalingam C <ramalingam.c@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220420181613.70033-3-matthew.auld@intel.com

drivers/gpu/drm/i915/selftests/i915_gem_gtt.c

@@ -1150,7 +1150,7 @@ static int misaligned_pin(struct i915_address_space *vm,
 		flags |= PIN_GLOBAL;
 
 	for_each_memory_region(mr, vm->i915, id) {
-		u64 min_alignment = i915_vm_min_alignment(vm, (enum intel_memory_type)id);
+		u64 min_alignment = i915_vm_min_alignment(vm, mr->type);
 		u64 size = min_alignment;
 		u64 addr = round_down(hole_start + (hole_size / 2), min_alignment);