input: touchscreen: synaptics_2.6: Add regulator configuration support

Add bus and power regulator configurations for both active
and suspend mode. Move to low power mode during idle suspend.
Enable configuration options through device tree.

Change-Id: Ic1509ab7e31e7488460a6cc86e5cd434a84fa7a8
Signed-off-by: Venkata Prahlad Valluru <vvalluru@codeaurora.org>