[UPDATED] WM97xx touchscreen drivers

[Mark Brown]

This patch series adds support for the touchscreen controllers provided
by Wolfson Microelectronics WM97xx series chips in both polled and
streaming modes.  It has been updated to reflect feedback since the
submission last week, most substantially in that the Makefile has been
cleaned up and the pxa-wm97xx has been renamed to mainstone-wm97xx to
better reflect how system-specific it is.