ARM: shmobile: lager: Enable SCIF0 and SCIF1 serial ports in DT

SCIF0 and SCIF1 are used as debug serial ports. Enable them and
configure pinmuxing appropriately. We can now remove the clkdev
registration hack for SCIF devices from the Lager reference board file.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
[horms+renesas@verge.net.au: updated changelog to remove references to
                             device renaming]
[horms+renesas@verge.net.au: resolved conflicts]
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>