aries | p1: staging: zram: make global var "devices" use unique name

The global variable "devices" is too general to be global.
This patch switches the name to be "zram_devices".

Signed-off-by: Noah Watkins <noahwatkins@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Humberto Borba <humberos@gmail.com>
Change-Id: I7fcc5a0f764080a0e51bf2a045501ddf9458a354