Recent changes caused the db845c to stop booting successfully,
and it was narrowed down to boringssl failures caused by us
missing the line to inherit updatable_apex.

This patch adds the line, and gets the board to boot again.

Change-Id: Ia56a4dc5eba92b6b044880782624b967b1baeb69
Signed-off-by: John Stultz <john.stultz@linaro.org>