linux-yocto-custom: Unblock overrides of linux-yocto.inc

linux-yocto.inc defines some overridable variable with ?=
and we do the same in the atmel recipes, and since linux-yocto.inc
is included before those overrides the ones from linux-yocto.inc
takes precedence. Lets fix it by delaying the inclusion until
after we have weakly defined them ourselves. Another way to fix
it would be to use hard assignments but we then can not override
them further in our own bbappends

Signed-off-by: Khem Raj <raj.khem@gmail.com>
linux-yocto-custom_3.6.9.bb: Point KBRANCH to a valid branch

Signed-off-by: Khem Raj <raj.khem@gmail.com>
at91bootstrap: Define AT91BOOTSTRAP_MACHINE

To make it possible to extend this recipe to atmel derivative
machines, lets no use MACHINE variable directly but instead
define AT91BOOTSTRAP_MACHINE which indicates same however
it can be overridden from other layers which makes it possible
to use the recipes for e.g. glomation SBCs which are atmel
based too.

Signed-off-by: Khem Raj <raj.khem@gmail.com>
at91bootstrap: Fix deploy dir

Use DEPLOYDIR instead of DEPLOY_DIR_IMAGE
Difference is that DEPLOYDIR is in the recipe's own
staging area, once we deploy it there the deploy
dependencies know how to stage it in final
deploy dir.

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Merge pull request #4 from kraj/master

linux-yocto-custom: Unblock overrides of linux-yocto.inc