MAINTAINERS: Update maintainer's mail address

Philipp has change the mail and the legacy one is not available, update it
to the new one.

CC: Philipp Tomsich <philipp.tomsich@vrull.eu>
Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/MAINTAINERS b/MAINTAINERS
index 4d0441c..86ff5e0 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -352,7 +352,7 @@
 
 ARM ROCKCHIP
 M:	Simon Glass <sjg@chromium.org>
-M:	Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
+M:	Philipp Tomsich <philipp.tomsich@vrull.eu>
 M:	Kever Yang <kever.yang@rock-chips.com>
 S:	Maintained
 T:	git https://source.denx.de/u-boot/custodians/u-boot-rockchip.git