hwspinlock/omap: add support for dt nodes

HwSpinlock IP is present only on OMAP4 and other newer SoCs,
which are all device-tree boot only. This patch adds the
base support for parsing the DT nodes, and removes the code
dealing with the traditional platform device instantiation.

Signed-off-by: Suman Anna <s-anna@ti.com>
[tony@atomide.com: ack for legacy file removal]
Acked-by: Tony Lindgren <tony@atomide.com>
[comment on the imperfect always-zero base_id]
Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com>