MAINTAINERS: Update STM32L4x5 and B-L475E-IOT01A maintainers

MAINTAINERS: Update STM32L4x5 and B-L475E-IOT01A maintainers

It has been a learning experience to contribute to QEMU for our
end-of-studies project. For a few months now, Arnaud and I aren't
actively involved anymore as we lack time and access to the hardware.
Therefore it's high time to update the maintainers file: from now on,
Samuel Tardieu who is behind the project will be taking up the role of
maintainer.

This commit updates maintainers and the list of files, and places the
two devices in alphabetical order.

Signed-off-by: Inès Varhol <ines.varhol@telecom-paris.fr>
Signed-off-by: Samuel Tardieu <sam@rfc1149.net>
Message-id: 20240921104751.43671-1-ines.varhol@telecom-paris.fr
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>