linux-wandboard (3.0.35): add recipe for 'official' wandboard kernel

Adds a recipe to build a kernel using the 'offical' wandboard
git repository.  Recipe is two parts.  linux-wandboard.inc specifies
items that should not change very often (SRCURI, LICENCE, and some
task append functions).  The .bb file specifies the SRCREV and
other things that could change quite often.
wandboard-dual: Make linux-wandboard preferred provider

With the addition of the linux-wandboard recipes, which build the
Wandboard kernel from the 'official' kernel source for Wandboard, change
the PREFERRED_PROVIDER to 'linux-wandboard'.
linux-imx (3.0.35): Remove wandboard from recipe

With the addition of the linux-wandboard recipe, we remove wandboard
support from the linux-imx recipes in order to prevent confusion and keep
all Wandboard effort focused on the 'official' Wandboard kernel.