ARM: k2g: Add support for dynamic programming of PLL based on SYSCLK

K2G supports various sysclk frequencies which can be
determined using sysboot pins. PLLs should be configured
based on this sysclock frequency. Add PLL configurations
for all supported sysclk frequencies.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>