ARM: OMAP4: Clock stubs since CLKDEV not in yet.

This patch update the common clock.c file for OMAP4. The clk_get() and
clk_put() functions are moved to  common place in arch/arm/common/clkdev.c
Since on current OMAP4 platform clk management is still not supported, the
platform file is stubbed with those functions.

Once the framework is ready, this WILL be replaced with a full
clkdev implementation.

Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>