ARM: shmobile: r8a7779: Use R8A7779_CLK_P as SCIF parent clock

Use R8A7779_CLK_P as parent clock for SCIF devices on r8a7779.
With this change in place the SCIF CCF handling matches the
legacy clock code. Also, this matches the data sheet.

Signed-off-by: Magnus Damm <damm+renesas@opensource.se>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>