omap3: Fix cpu detection

We need to set the omap_chip.oc carefully for the clocks to work.

To fix this, set the omap_chip.oc in omap3_check_features() based
on the CONTROL_IDCODE and silicon revision registers.

Also add handling for 34xx es3.1.2 as es3.1 for now.

Fixes booting on at least overo board.

Based on an earlier patch by Paul Walmsley <paul@pwsan.com>.

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