ARM: dts: OMAP: Add #hwlock-cells property to hwspinlock nodes

Add a new generic property "#hwlock-cells" to the hwspinlock
DT nodes on OMAP4, OMAP5 and AM33xx. This common property allows
different platform implementations to define the args specifier
length. OMAP implementations will always use a value of 1.

Signed-off-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>