Add I2C4 clock support for i.MX6SX. Since we use runtime check,
but not macro, we need to remove `#ifdef ..` in crm_regs.h, or
gcc will fail to compile the code succesfully.
Making the macros only for i.MX6SX open to other i.MX6x maybe not
a good choice, but we have runtime check.
Signed-off-by: Peng Fan <Peng.Fan@freescale.com>
19c6ec70c5