cpufreq: OMAP: move clk name decision to init

Clk name does'nt need to dynamically detected during clk init.
move them off to driver initialization, if we dont have a clk name,
there is no point in registering the driver anyways. The actual clk
get and put is left at cpu_init and exit functions.

Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Kevin Hilman <khilman@ti.com>