ARM: shmobile: r8a73a4 SCIF support V3

V3 of SCIF serial port support for the r8a73a4 SoC.
This is done by adding platform devices for SCIFA0
-> SCIFA1 as well as SCIFB0 -> SCIFB3 together with
clock bindings. DT device description is excluded at
this point since such bindings are still under
development.

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>