Maintainers: add myself as reviewer for sbsa-ref

At Linaro I work on sbsa-ref, know direction it goes.

May not get code details each time.

Signed-off-by: Marcin Juszkiewicz <marcin.juszkiewicz@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20230515143753.365591-1-marcin.juszkiewicz@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

MAINTAINERS

@@ -940,6 +940,7 @@ SBSA-REF
 M: Radoslaw Biernacki <rad@semihalf.com>
 M: Peter Maydell <peter.maydell@linaro.org>
 R: Leif Lindholm <quic_llindhol@quicinc.com>
+R: Marcin Juszkiewicz <marcin.juszkiewicz@linaro.org>
 L: qemu-arm@nongnu.org
 S: Maintained
 F: hw/arm/sbsa-ref.c