At some point while adding omap2 support, IS_OMAP_CLASS broke as pointed out
by Russell King. Fix this to work as it used to work, and modify omap24xx and
omap34xx detection to work accordingly.

Also rename OMAP3430_REV_ES2_2 to OMAP3430_REV_ES3_0.
Signed-off-by: Tony Lindgren <tony@atomide.com>