phy: renesas: rcar-gen3-usb2: change a condition "dr_mode"

This patch changes a condition about dr_mode. If a device node has
any dr_mode ("host", "peripheral" or "otg"), this driver allows to
set "is_otg_channel" to true. Also, this patch keeps the dr_mode
value for future use.

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>