In order to snapshot memory, interrupts must be disabled. However, in order
to write the saved image to disk, interrupts must be re-enabled and devices
resumed. Previously, both actions were called from swsusp_arch_suspend().

This patch separates those two actions has only the snapshotting routine 
called from swsusp_arch_suspend(). swsusp now handles it's own disabling of
interrupts only for the time required. This is now handled from swsusp_save()
and swsusp_write() now handles writing the image only (called with interrupts
enabled).

swsusp_save_image() was renamed to swsusp_suspend() (and the old incarnation
deleted since it was simply a wrapper).