Add a new OMAP chip identification interface, omap_chip_id.
omap_chip_id is a structure which contains one bit for each OMAP2/3
CPU type, and on 3430, ES level.  For example, the CHIP_IS_OMAP2420
bit is set in omap_chip at boot on an OMAP2420.  On OMAP3430ES2, both
CHIP_IS_OMAP3430 and CHIP_IS_OMAP3430ES2 bits are set.

omap_chip is set in mach-omap2/id.c by _set_omap_chip(). Other
code should use the omap_chip_is() function to test against omap_chip.

Also, clean up id.c by splitting some code out of
omap_check_revision() into its own function, _set_system_rev(); and
converting some debug printk()s into pr_debug().

Second revision.
Signed-off-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>