dm: core: add support for getting register address and size

dm: core: add support for getting register address and size

Current dev_read_*() API lacks support to get address and size
of a "reg" property by name or index. Add support for the same.

Livetree support has been added but not tested on real hardware.

The existing unit tests testing reading address from device-tree
have been updated to test address as well as size.

Reviewed-by: Lokesh Vutla <lokeshvutla@ti.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>