staging: android: Add more help description on Kconfig

This patch adds more help description on android Kconfig for
- lowmemory killer
- Timed gpio (same for timed output)

Signed-off-by: Jagan Teki <jteki@openedev.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Brian Swetland <swetland@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>