Add DT OPP table for OMAP34xx/35xx family of devices. This data is
decoded by OF with of_init_opp_table() helper function.
OPP data here is based on existing opp3xxx_data.c
Since the omap36xx OPP tables would be different from OMAP34xx/35xx,
introduce an new omap34xx.dtsi for 34xx/35xx specific entries and use
existing omap3.dtsi as the common dtsi file for all OMAP3 platforms.
This is in preparation to use generic cpufreq-cpu0 driver for device
tree enabled boot. Legacy non device tree enabled boot continues to
use omap-cpufreq.c and opp3xxx_data.c.