ARM: imx: set up pllv3 POWER and BYPASS sequentially

Currently, POWER and BYPASS bits are set up in a single write to pllv3
register.  This causes problem occasionally from the IPU/HDMI testing.
Let's follow FSL BSP code to set up POWER bit, relock, and then BYPASS
sequentially.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>