edison: add mmap support. read & write

Closes #27

Signed-off-by: Thomas Ingleby <thomas.c.ingleby@intel.com>
galileo gen 1: port mmap to new structure

Signed-off-by: Thomas Ingleby <thomas.c.ingleby@intel.com>
galileo gen 2: port mmap to new structure

Feature parity pre mem branch.

Signed-off-by: Thomas Ingleby <thomas.c.ingleby@intel.com>