treewide: Add missing includes ...

A lot of files rely on include/driver.h including include/of.h (and
this including include/errno.h. include the files explicitly so we can
eventually get rid of including of.h from driver.h

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

add filetype command support ...

This adds support for a filetype detection command. It can be
used to print a filename on the console or to set a variable
with the detection result for use in shell scripts.
The command also has an option to print the known filetypes
so that a user knows what to match for.

Based on an earlier version from Jean-Christophe.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>