payloads/depthcharge: Specify revision to build

Add the capability for specifying which version of depthcharge to
checkout and build.  This is similar to the existing feature for
SeaBIOS.

The depthcharge makefile already contains some structure for checking
out master vs. stable however the calling Makefile.inc ingored this
feature.  Add the command-line variable assignment for these, along
with a tree-ish for any revision.

Change-Id: I99a5b088cb0ebb29e5d96a84217b3bfa852de8ac
Signed-off-by: Marshall Dawson <marshalldawson3rd@gmail.com>
Reviewed-on: https://review.coreboot.org/18270
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Martin Roth <martinroth@google.com>
3 files changed