staging: android: persistent_ram: Prepare for modular builds

This is a transition patch to keep things bisectable, just moves
some routines under '#ifndef MODULE'. The code inside the #ifndef
will go away soon, but so far we must support pstore and ram_console.

So, we are about to use persistent_ram with pstore, with the ability
to compile persistent_ram routines as modules. Some parts of
persistent_ram uses memblock_reserve() routine, which is should be
only used built-in code, and thus it is not exported.

These persistent_ram bits are only used by Android's ram_console,
which is always built-in.

Without this patch, we won't able to compile persistent_ram as a
module:

ERROR: "memblock_reserve" [fs/pstore/ramoops.ko] undefined!
make[1]: *** [__modpost] Error 1
make: *** [modules] Error 2

(As alternative, we could export memblock_reserve, but the thing
is: we won't need it later.)

Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>