ARM: shmobile: r8a7790: switch from scif to scifa

SCIF and SCIFA can be plexed onto the same wires on Lager board. The
datasheet also describes the wires as SCIFA. So, to make use of the
bigger FIFOs switch to SCIFA instead.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>