MX5: Modify the PLL decoding algorithm

The PLL decoding algorithm didn't take into account many configuration bits.
Adjust it according to Linux kernel. Also, add PLL4 for MX53.

Signed-off-by: Marek Vasut <marek.vasut@gmail.com>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Jason Hui <jason.hui@linaro.org>
Tested-by: Jason Liu <Jason.hui@linaro.org>