ARM: shmobile: R-Mobile: Consolidate rmobile_pd_suspend_*()

Consolidate the identical rmobile_pd_suspend_*() routines that just
return -EBUSY to prevent a PM domain from being powered down into a
single rmobile_pd_suspend_busy().

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