MAINTAINERS: add mst to list of biosbits maintainers

Adding Michael's name to the list of bios bits maintainers so that all changes
and fixes into biosbits framework can go through his tree and he is notified.

Suggested-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Ani Sinha <ani@anisinha.ca>
Message-Id: <20221111151138.36988-1-ani@anisinha.ca>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

MAINTAINERS

@@ -1865,6 +1865,7 @@ F: hw/acpi/viot.h
 
 ACPI/AVOCADO/BIOSBITS
 M: Ani Sinha <ani@anisinha.ca>
+M: Michael S. Tsirkin <mst@redhat.com>
 S: Supported
 F: tests/avocado/acpi-bits/*
 F: tests/avocado/acpi-bits.py