Staging: android: Remove pmem driver

Addroid pmem driver is no longer used in any of the Android products.
This patch removes pmem driver from Android staging area

Reference: https://lkml.org/lkml/2012/1/23/183



Signed-off-by: Shuah Khan <shuahkhan@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>