phy: rcar-gen3-usb2, rcar-gen2: Use ARCH_RENESAS

Make use of ARCH_RENESAS in place of ARCH_SHMOBILE.
A now redundant dependency on OF is also dropped.

This is part of an ongoing process to migrate from ARCH_SHMOBILE to
ARCH_RENESAS the motivation for which being that RENESAS seems to be a more
appropriate name than SHMOBILE for the majority of Renesas ARM based SoCs.

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