ARM: shmobile: r7s72100 clock: Add RSPI clocks for DT

Add DT-style ("%08x.spi") clocks, as Genmai doesn't use the common
clock framework yet.

Signed-off-by: Geert Uytterhoeven <geert+renesas@linux-m68k.org>
Acked-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>