lint: Move the lint script out of Makefile.inc

In preparation for adding junit xml to the lint tests, move the
script out of Makefile.inc and into its own file.

Add a copyright, usage, and error checking that was not needed
inside the Makefile.

Change-Id: I32bebc6a5f1f6fa652812c8a014d84006e2e6c8a
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: http://review.coreboot.org/11890
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
2 files changed