Follow the usual pattern of devices registration by adding new function
(wpan_phy_set_dev) that sets child->parent relationship and removing
parent argument from wpan_phy_register call.
Signed-off-by: NDmitry Eremin-Solenikov <dbaryshkov@gmail.com>

IEEE 802.15.4-2006 defines channel pages that hold channels (max 32 pages,
27 channels per page). Allow the driver to specify supported channels
on pages, other than the first one.
Signed-off-by: NDmitry Eremin-Solenikov <dbaryshkov@gmail.com>

Use snprintf to limit the amount of chars put in the buffer for attr -> show.
Signed-off-by: NDmitry Eremin-Solenikov <dbaryshkov@gmail.com>

Set page to zero (for compatibility w/ devices supporting only first page).
Also init channel by default to -1 to disallow transfers for non-initialised
devices.
Signed-off-by: NDmitry Eremin-Solenikov <dbaryshkov@gmail.com>

Add API to iterate over the wpan-phy instances.
Signed-off-by: NDmitry Eremin-Solenikov <dbaryshkov@gmail.com>

Add a sysfs/in-kernel representation of LR-WPAN master devices.
Signed-off-by: NDmitry Eremin-Solenikov <dbaryshkov@gmail.com>