pca953x: add power management support

Add suspend/resume functionality to PCA953x driver.
Limitation:
Seemingly does not satisfy PCA957x (also covered by pca953x.c)
requirements.

Restore PCA953x state, overriding the default state preset upon
power-up.

This patch was originally authored by Saeed Bishara of Marvell.
Reference:
https://lists.ubuntu.com/archives/kernel-team/2009-August/007035.html

Signed-off-by: Andrey Gelman <andrey.gelman@compulab.co.il>
sb-fx6: pca953x: enable DVI transmitter

Enable DVI transmitter by default.
In the past, DVI transmitter has been enabled accidentally, due to
pca953x eGPIO default state (input with a pull-up resistor).

Additionally, set e few more eGPIO(s).

Signed-off-by: Andrey Gelman <andrey.gelman@compulab.co.il>