MAINTAINERS: update Lorenzo's email address

Using my kernel.org email.

Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/e98fcf759f8c23a9736f1c4d20ca0437e4b145de.1648120046.git.lorenzo@kernel.org