PM / shmobile: Don't include SH7372's INTCS in syscore suspend/resume

Since the SH7372's INTCS in included into syscore suspend/resume,
which causes the chip to be accessed when PM domains have been
turned off during system suspend, the A4R domain containing the
INTCS has to stay on during system sleep, which is suboptimal
from the power consumption point of view.

For this reason, add a new INTC flag, skip_syscore_suspend, to mark
the INTCS for intc_suspend() and intc_resume(), so that they don't
touch it.  This allows the A4R domain to be turned off during
system suspend and the INTCS state is resrored during system
resume by the A4R's "power on" code.

Suggested-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Magnus Damm <damm@opensource.se>