usb: host: xhci-rcar: Use xhci_plat_priv.quirks instead of code settings

This patch uses xhci_plat_priv.quirks to simplify. The previous
code had conditions to set some quirks in xhci_rcar_init_quirk().
But, the xhci_rcar_init_quirk() is called at the same conditions.
So, no behavior change.

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/1567425698-27560-4-git-send-email-yoshihiro.shimoda.uh@renesas.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>