clk: renesas: Add R-Car X5H CPG SCMI remapping driver

Add a proof-of-concept Clock Pulse Generator driver for the R-Car X5H
(R8A78000) SoC, using tables to remap from hardware clock IDs to SCMI
clock IDs.

Some SCMI clocks do not support the SCMI CLOCK_ATTRIBUTES command, and
are thus not usable from Linux.  Register a bunch of fixed-rate clocks,
and use them as replacements for SCMI clocks that are known to be
unusable.

For now this contains preliminary support for SCP FW SDKv4.28.0,
v4.31.0, and v4.32.0.  As SCMI clock IDs are identical for SDKv4.31.0
and v4.32.0, r8a78000_cpg_fw_4_31_0[] applies to both of them.

Suggested-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>