MAINTAINERS: update Michal Simek's email

@xilinx.com is still working but better to switch to new amd.com after
AMD/Xilinx acquisition.

Link: https://lkml.kernel.org/r/bd073d026f8c367a9cfb45d26d39f26e40c665dc.1683035692.git.michal.simek@amd.com
Signed-off-by: Michal Simek <michal.simek@amd.com>
Cc: Colin Ian King <colin.i.king@gmail.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Kirill Tkhai <tkhai@ya.ru>
Cc: Konrad Dybcio <konrad.dybcio@linaro.org>
Cc: Qais Yousef <qyousef@layalina.io>
Cc: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>