Add and enable the external crystal for the SCIF_CLK and its pinctrl, to
be used by the Baud Rate Generator for External Clock (BRG) on (H)SCIF.

This increases the range and accuracy of supported baud rates:
  - SCIF:
      - Supports now 50, 75, 110, 1152000, 1500000, 2000000, and
        4000000 bps,
      - Perfect match for standard 50-460800, and 9216000 bps.
      - More accurate 576000 bps.
  - HSCIF:
      - Supports now 50, 75, 110, 134, 150, and 200 bps,
      - Perfect match for standard 50-460800, and 9216000 bps.
      - More accurate 576000, 1152000, 3000000, 3500000, and 4000000
	bps.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>