ARM: S5P6440: Remove usage of clk_h and add clk_hclk clock

The clk_h clock is of type 'struct clk' whereas on S5P6440,
the hclk is more suitable to be of type 'struct clksrc_clk'
(since hclk clock is divided version of armclk)

This patch modifies the following.

1. Adds the 'clk_hclk' clock which is of type 'struct clksrc_clk'.
2. Removes all references to the clk_h clock.
3. Addes clk_hclk into the list of sysclks.
4. The clock rate 'hclk' is modified to be derived from clk_hclk.

Signed-off-by: Thomas Abraham <thomas.ab@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>