MAINTAINERS: Add a file to MIPS section

File tests/acceptance/linux_ssh_mips_malta.py is crucial for
entire MIPS platform, so add it to the MIPS section. The
maintainership will be shared with others.
Signed-off-by: NAleksandar Markovic <amarkovic@wavecomp.com>
Message-Id: <1575982519-29852-6-git-send-email-aleksandar.markovic@rt-rk.com>

MAINTAINERS

@@ -221,6 +221,7 @@ F: include/hw/intc/mips_gic.h
 F: include/hw/mips/
 F: include/hw/misc/mips_*
 F: include/hw/timer/mips_gictimer.h
+F: tests/acceptance/linux_ssh_mips_malta.py
 F: tests/tcg/mips/
 K: ^Subject:.*(?i)mips