MAINTAINERS: Update email address

Update my email address in the MAINTAINERS file as  the current
one will stop functioning in a while.

Signed-off-by: Thara Gopinath <thara.gopinath@linaro.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>