rpi-first-run-wizard: remove

The existing first run script is inappropriate for a board support layer. It is
also full of references to OpenPandora and is not portable across all distros
which may use meta-raspberrypi.

Signed-off-by: Paul Barker <paul@paulbarker.me.uk>
bootfiles, vc-graphics: consolidate SRC_URI and S variables

The variables RPIFW_SRC_URI and RPIFW_S are created in the common firmware
include file so that it is easier to override the firmware source in a local or
distro config file. RPIFW_SRC_URI is used to set SRC_URI in firmware.inc as it
is common to both bootfiles and vc-graphics. RPIFW_S is used as a prefix for S
in bcm2835-bootfiles.bb and vc-graphics.inc as different subdirectories are
referenced in each recipe.

Signed-off-by: Paul Barker <paul@paulbarker.me.uk>
psplash: only set image for MACHINE=raspberrypi

Instead of overriding the default psplash image, the raspberrypi image is added
as an additional image. It is then set as the default in the raspberrypi machine
config file so that other targets do not pick up our splash image.

Tested on raspberrpi and qemuarm: on raspberrypi I see to Raspberry Pi logo, on
qemuarm I see the Yocto Project logo.

Signed-off-by: Paul Barker <paul@paulbarker.me.uk>