usb: renesas_usbhs: tidyup for smatch warnings

This patch tidyup below smatch complaint

drivers/usb/renesas_usbhs/mod_host.c +447 usbhsh_endpoint_free()
	 warn: variable dereferenced before check 'uep' (see line 444)

Special thanks to Dan

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>