docs: add edison to supported platforms.

Signed-off-by: Thomas Ingleby <thomas.c.ingleby@intel.com>
Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>
aio: add init hooks, and fp hook

Signed-off-by: Thomas Ingleby <thomas.c.ingleby@intel.com>
Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>
aio: internal aio context to mraa_internal_types

* Some comments for members of structure also added

Signed-off-by: Thomas Ingleby <thomas.c.ingleby@intel.com>
Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>
hook: add pwm hook around init

Signed-off-by: Thomas Ingleby <thomas.c.ingleby@intel.com>
Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>
hook: add spi init hooks

Signed-off-by: Thomas Ingleby <thomas.c.ingleby@intel.com>
Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>