bus: mhi: ep: check the correct variable in mhi_ep_register_controller()

There is a copy and paste bug here so it checks "ev_ring_el_cache" instead
of "ring_item_cache".

Fixes: 62210a26 ("bus: mhi: ep: Use slab allocator where applicable")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://lore.kernel.org/r/bebcd822-d465-45da-adae-5435ec93e6d4@moroto.mountainSigned-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

drivers/bus/mhi/ep/main.c

@@ -1497,7 +1497,7 @@ int mhi_ep_register_controller(struct mhi_ep_cntrl *mhi_cntrl,
 	mhi_cntrl->ring_item_cache = kmem_cache_create("mhi_ep_ring_item",
 							sizeof(struct mhi_ep_ring_item), 0,
 							0, NULL);
-	if (!mhi_cntrl->ev_ring_el_cache) {
+	if (!mhi_cntrl->ring_item_cache) {
 		ret = -ENOMEM;
 		goto err_destroy_tre_buf_cache;
 	}