lttng-modules: fix build against 5.15+

When testing linux-yocto-dev 5.15-rc, lttng-modules fails to build.
Upstream already has fixes for 5.15 in the release branch, so we
backport the two patches here and we can drop them on the next version
bump.

Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>