input: synaptics_i2c_rmi4: Add device tree support

To work with device tree framework, support must be added
in driver.  Read in properties such as gpios, x/y size and
soft button mapping.  Also, enable multitouch with protocol
b.

This patch is a propagated patch from 3.4 kernel
commit - ecfb48913f4a3f27913140eceae619336919b6fd,
input: synaptics_i2c_rmi4: Add device tree support

Change-Id: I17f41105c57f22db1623d03627ca89f47ef57a8b
Signed-off-by: Amy Maloche <amaloche@codeaurora.org>
Signed-off-by: Abinaya P <abinayap@codeaurora.org>