clk: renesas: r8a779f0: Add SASYNCPER internal clock

Add the SASYNCPER internal clock, which is the clock source of the
various SASYNCPERD[124] clocks, to match the clock tree diagram in the
documentation.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reported-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://lore.kernel.org/r/18e6765bfc3bf7c3ee5ce93a370d377c1d17728e.1665558014.git.geert+renesas@glider.be