omap: mailbox: Add resources and mailbox register base address for OMAP4 mailbox

This patch adds resource information of mailbox driver for
OMAP4 mailbox module. Register base address also added

Signed-off-by: C A Subramaniam <subramaniam.ca@ti.com>
Signed-off-by: Ramesh Gupta G <grgupta@ti.com>
Acked-by: Hiroshi DOYU <Hiroshi.DOYU@nokia.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>