ARM: shmobile: Remove obsolete legacy PM Domain leftovers

The last users were removed in commit b5872880 ("ARM: shmobile:
R-Mobile: Remove legacy PM Domain code").

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