davinci: omapl138_lcdk: increase PLL0 frequency

The LCDC controller on the lcdk board has high memory throughput
requirements. Even with the kernel-side tweaks to master peripheral
and peripheral bus burst priorities, the default PLL0 frquency of
300 MHz is not enough to service the LCD controller and causes
DMA FIFO underflows.

Increment the PLL0 multiplier to 37, resulting in PLL0 frequency of
456 MHz - the same value that downstream reference u-boot from Texas
Instruments uses.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Reviewed-by: Tom Rini <trini@konsulko.com>