android: persistent_ram: fix section mismatch in clients

persistent_ram clients will call the init functions from their
probe functions, which need to be __devinit, not __init.  Change
the persistent_ram init functions to be __devinit.

Signed-off-by: Colin Cross <ccross@android.com>

Change-Id: If92338f7c8d57dd34b286ff7705a96c078477ba4