dm: pinctrl: Use explicit values for enums

Based on discussion at
https://lore.kernel.org/r/20200318125003.GA2727094@kroah.com

 we got
recommendation to use explicit values for all enums.

So, add explicit values to all pinctrl related enums for readability.

Signed-off-by: Ashok Reddy Soma <ashok.reddy.soma@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Link: https://lore.kernel.org/r/dcdb20e7252ea7465e9f984d815e9624c30e9558.1645624969.git.michal.simek@xilinx.com