drivers: sh: Stop using the legacy clock domain on ARM

Since commits 71d076ce ("ARM: shmobile: Enable PM and
PM_GENERIC_DOMAINS for SoCs with PM Domains") and 2ee98234


("arm64: renesas: Enable PM and PM_GENERIC_DOMAINS for SoCs with PM
Domains"), CONFIG_PM and CONFIG_PM_GENERIC_DOMAINS are enabled
unconditionally for Renesas ARM-based SoCs. Hence the legacy clock
domain is no longer used on these SoCs.

Remove the related support code, and stop entering drivers/sh/ on ARM.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>