soc: renesas: r8a779g0-sysc: Add missing A3DUL power domain

Add the power domain structure for the A3DUL domain (PAP-Subsystem), as
described in the R-Car V4H Series Hardware User's Manual Rev. 0.51 and
later.

Signed-off-by: Tam Nguyen <tam.nguyen.xa@renesas.com>
[geert: Manual reference]
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Link: https://lore.kernel.org/r/14bd8a8de16ced703ff824f6a241e89d1ead6b07.1669740926.git.geert+renesas@glider.be