ARM: OMAP3+: use cpu0-cpufreq driver in device tree supported boot

With OMAP3+ and AM33xx supported SoC having defined CPU device tree
entries with operating-points and clock nodes defined, we can now use
the SoC generic cpufreq-cpu0 driver by registering appropriate device.

Cc: Benoit Cousson <bcousson@baylibre.com>
Cc: Kevin Hilman <khilman@deeprootsystems.com>
Cc: Paul Walmsley <paul@pwsan.com>
Cc: Tony Lindgren <tony@atomide.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>