aries | p1: staging: zsmalloc documentation

Documentation of various struct page fields
used by zsmalloc.

Changes for v2:
	- Regroup descriptions as suggested by Konrad

Change-Id: I39b79c8d9f735d1464926b7a20ab71e908c70cb4
Signed-off-by: Nitin Gupta <ngupta@vflare.org>
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Humberto Borba <humberos@gmail.com>

Change-Id: I39b79c8d9f735d1464926b7a20ab71e908c70cb4