MAINTAINERS: Add a git tree for the stm class

So that people know where their patches go.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Reviewed-by: Laurent Fert <laurent.fert@intel.com>

MAINTAINERS

@@ -9742,6 +9742,7 @@ F:	drivers/mmc/host/dw_mmc*
 SYSTEM TRACE MODULE CLASS
 M:	Alexander Shishkin <alexander.shishkin@linux.intel.com>
 S:	Maintained
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/ash/stm.git
 F:	Documentation/trace/stm.txt
 F:	drivers/hwtracing/stm/
 F:	include/linux/stm.h