arm: socfpga: Restructure clock manager driver

Restructure clock manager driver in the preparation to support A10.
Move the Gen5 specific code to _gen5 files.

- Change all uint32_t to u32 and change to use macro BIT(n) for bit shift.
- Check return value from wait_for_bit(). So change return type to int for
  cm_write_with_phase() and cm_basic_init().

Signed-off-by: Ley Foon Tan <ley.foon.tan@intel.com>