ARM: shmobile: r8a7740: Add A3RV pm domain support

Add support for the A3RV power domain.
This domain contains the VPU5F and VCP1 hardware blocks, which are
currently not used by any driver.

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