Dump memory going from unreadable to readable.

If the first read when dumping memory returns no data, skip ahead to
the next page boundary and try and read from there. This fixes a case
where the address at which to start dumping memory is unreadable, but
crosses back into readable memory.

Bug: 22234753
Change-Id: Ie28d5c027013577ca06f5396aba498366a3b6749