dt-bindings: Synchronize R-Car Gen3 headers with Linux 5.2

Backport and squash below Linux v5.2 commits:

Commit id       *  Summary line
da3e1c57caf93e [1] soc: renesas: r8a77970-sysc: Remove non-existent CR7 power domain
b5eb730e031aca [1] soc: renesas: r8a77970-sysc: Correct names of A2DP/A2CN power domains
3961d355dfb512     dt-bindings: power: r8a77965: Remove non-existent A3IR power domain

(*) Patch id mismatch between Linux and U-Boot commit
[1] Dropped changes in drivers/soc/renesas/r8a77970-sysc.c,
    since the file doesn't exist in U-Boot.

Signed-off-by: Eugeniu Rosca <erosca@de.adit-jv.com>