ARM: AM33xx: Cleanup dplls data

Locking sequence for all the dplls is same.
In the current code same sequence is done repeatedly
for each dpll. Instead have a generic function
for locking dplls and pass dpll data to that function.

This is derived from OMAP4 boards.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Tested-by: Heiko Schocher <hs@denx.de>
Acked-by: Heiko Schocher <hs@denx.de>