Adds a recipe for the rpi-6.18.y branch of the raspberrypi/linux
tree alongside the existing 6.1, 6.6 and 6.12 recipes.
Note that 6.18 is not yet considered stable on Raspberry Pi OS:
upstream has not cut a stable_* tag against this series and users
are still reporting regressions on the Raspberry Pi forums. The
default kernel is therefore intentionally left at 6.12 in
conf/machine/include/rpi-default-versions.inc; opt in by setting
PREFERRED_VERSION_linux-raspberrypi to "6.18.%".
https://github.com/raspberrypi/linux/tree/rpi-6.18.y
Signed-off-by: Paolo Barbolini <paolo.barbolini@m4ss.net>
Paolo Barbolini