init: move initial property area allocation into bionic

bionic's __system_property_add() now expands the property area as needed
by mapping in more pages.  Rather than duplicate the mapping code, move
it inside bionic and have bionic's __system_property_area_init() set up
the first page.

Signed-off-by: Greg Hackmann <ghackmann@google.com>

(cherry picked from commit f14eef0c3c456bfe39f7e9d57c8f7ae4ec775972)

Change-Id: Ieb94caab1527c71f2155efe3795490b0ea215a29