nvram: Add a get_max_space_size_in_bytes method.

This is useful for the Access-Controlled NVRAM HAL because
implementations may be able to achieve atomic writes if they are able to
limit the maximum space size. This method allows the module to report
that it is imposing such a limit.

BUG=27480753

Change-Id: Ia70f459d7d5fca894e52310ddb2cdcbb51bd8364
1 file changed