feat(rcar): rewrite SCIF driver from assembler to C

Rewrite the SCIF driver from difficult to read assembler to plain C.
Use scif-common.c which contains putc() and flush() helper functions
to avoid duplication, so only fill in the initialization code. Drop
support for external clock, which is unused. Clean up macros and drop
ones which are not referenced.

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Change-Id: Ia933c505c33e133e45448c82776a17629f3df1eb
4 files changed