meta-agl-bsp: Enable WIC support for Raspberry Pi 2/3

In order to have WIC images be fully functional for both u-boot and
non-u-boot we need to bring in more logic in determining what files will
get mapped to what location.  This is not found in meta-raspberrypi/pyro
but is found in their master branch.  These changes bring us in sync
with meta-raspberrypi/conf/machine/include/rpi-base.inc as of their
revision c26e9d3df54293a88fba047a29b335f52b01120e for Pi 2 and Pi 3.  We
do not attempt to bring in the additional logic they have to handle
Pi 3-64 and U-Boot at this time as that is more invasive and not
required for our use cases.

Bug-AGL: SPEC-409
Change-Id: I642735a9be3daad96c0c1376cd6341b0697ffc09
Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/11207
Tested-by: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
ci-image-build: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
ci-image-boot-test: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>