Reduce the size of struct clk by 12 bytes and make defining clocks with
common implementation functions easier by moving the set_rate, get_rate,
round_rate and set_parent calls into a new structure called 'struct clk_ops'
and using that instead.

This change does make a few clocks larger as they need their own clk_ops,
but this is outweighed by the number of clocks with either no ops or having
a common set of ops.

Update all the users of this.
Signed-off-by: NBen Dooks <ben-linux@fluff.org>