ARM: OMAP2+: PM: share some suspend-related functions across OMAP2, 3, 4

The platform_suspend_ops can be shared across OMAP2, 3, and 4, along
with all of the functions referenced in that structure.  This patch
shares them.  It also removes the suspend_state file-scoped variable
in the OMAP2 and 3 PM code; it does not appear to be actually needed
by anything.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Cc: Santosh Shilimkar <santosh.shilimkar@ti.com>
Cc: Rajendra Nayak <rnayak@ti.com>
Reviewed-by: Kevin Hilman <khilman@ti.com>
[khilman@ti.com: minor rework needed due to rebase/merge with conflicting changes]
Signed-off-by: Kevin Hilman <khilman@ti.com>