FROMLIST: binder: separate binder allocator structure from binder proc

(from https://patchwork.kernel.org/patch/9817745/

)

The binder allocator is logically separate from the rest
of the binder drivers. Separating the data structures
to prepare for splitting into separate file with separate
locking.

Change-Id: I5ca4df567ac4b8c8d6ee2116ae67c0c1d75c9747
Signed-off-by: Todd Kjos <tkjos@google.com>