MAINTAINERS: Add 'Performance Tools and Tests' subsection

MAINTAINERS: Add 'Performance Tools and Tests' subsection

This commit creates a new 'Miscellaneous' section which hosts a new
'Performance Tools and Tests' subsection. This subsection will contain
the the performance scripts and benchmarks written as a part of the
'TCG Continuous Benchmarking' project. Also, it will be a placeholder
for follow-ups to this project, if any.

Signed-off-by: Ahmed Karaman <ahmedkhaledkaraman@gmail.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Aleksandar Markovic <aleksandar.qemu.devel@gmail.com>
Signed-off-by: Aleksandar Markovic <aleksandar.qemu.devel@gmail.com>
Message-Id: <20200626164546.22102-4-ahmedkhaledkaraman@gmail.com>