usb: usb251xb: Use of_property_read_u16()

Use of_property_read_u16() instead of of_property_read_u16_array() when
only 1 element is read.
This slightly simplifies the code.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Message-ID: <97478908a814d4fa694e0ca44212c3776cf3e6e9.1685877052.git.christophe.jaillet@wanadoo.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>