usb: renesas_usbhs: fix error return code of usbhsf_pkt_handler()

When __usbhsf_pkt_get() returns NULL to pkt, no error return code of
usbhsf_pkt_handler() is assigned.
To fix this bug, ret is assigned with -EINVAL in this case.

Reported-by: TOTE Robot <[e-mail]>
Signed-off-by: Jia-Ju Bai <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/renesas_usbhs/fifo.c

···
 	usbhs_lock(priv, flags);
 
 	pkt = __usbhsf_pkt_get(pipe);
-	if (!pkt)
+	if (!pkt) {
+		ret = -EINVAL;
 		goto __usbhs_pkt_handler_end;
+	}
 
 	switch (type) {
 	case USBHSF_PKT_PREPARE: