block: gendisk: Add a new flag in gendisk structure

Add a new flag in gendisk structure to serialize offsets
for swap partition. This flag is enabled for the gendisk of
the block device which will be used for saving the snapshot
of the hibernation image, based on a kernel parameter
"noswap_randomize". Serializing offset in swap partition
helps in improving hibernation resume time from bootloader.

Change-Id: I52ecd078fd47ff6f47b7eff27ee8333a3aac85f8
Signed-off-by: Vivek Kumar <vivekuma@codeaurora.org>