Update email addresses of Aleksandar Markovic and Paul Burton in the
MAINTAINERS file. Also, add corresponding items in the .mailmap file.

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Aleksandar Markovic <amarkovic@wavecomp.com>