Add McBSP hwmod data for OMAP2420.

Also add macros in prcm-common.h for idlest bit of OMAP24XX McBSP devices
Signed-off-by: Charulatha V <charu@ti.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Shubhrajyoti D <shubhrajyoti@ti.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>