wandboard.inc: add file with common settings for wandboard boards

Currently the following variables can be shared among all the
wandboard models: PREFERRED_PROVIDER_virtual/kernel, SERIAL_CONSOLE
and MACHINE_FEATURES.  Move them to a include file to avoid code
duplication.

Signed-off-by: Mario Domenech Goulart <mario@ossystems.com.br>
wandboard.inc: add touchscreen support

Signed-off-by: Mario Domenech Goulart <mario@ossystems.com.br>