omap: add hwspinlock device

Build and register an hwspinlock platform device.

Although only OMAP4 supports the hardware spinlock module (for now),
it is still safe to run this initcall on all omaps, because hwmod lookup
will simply fail on hwspinlock-less platforms.

Signed-off-by: Simon Que <sque@ti.com>
Signed-off-by: Hari Kanigeri <h-kanigeri2@ti.com>
Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Kevin Hilman <khilman@ti.com>
Cc: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>