arm/dts: OMAP3: Add omap3evm and am335xevm support

TI's OMAP3EVM and AM335xEVM are software development boards
available for OMAP35x(AM/DM37x) and AM335x devices respectively;
and these devices are considered under omap3 family.

Signed-off-by: Vaibhav Hiremath <hvaibhav@ti.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Tony Lindgren <tony@atomide.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>