linux-raspberrypi-dev: Update for testing v5.10.y
linux-raspberrypi-dev: Update for testing v5.10.y

Linux 5.10 series will be the next LTS kernel so it's likely to be the
new stable branch for linux-raspberrypi within a couple of months. Let's
get set up to test it now.

Signed-off-by: Paul Barker <ea07171fd37de70b22964565a4c2bfd2bb2b3061@konsulko.com>

agherzan/meta-raspberrypi,schnitzeltony/meta-raspberrypi,agherzan/meta-raspberrypi,schnitzeltony/meta-raspberrypi,agherzan/meta-raspberrypi,schnitzeltony/meta-raspberrypi,agherzan/meta-raspberrypi,agherzan/meta-raspberrypi,agherzan/meta-raspberrypi