MAINTAINERS: Add maintenance information for psi

Add a maintainer section for psi, as it's a user-visible, configurable
kernel feature.

The patches are still routed through the scheduler tree due to the
close integration with that code, but get_maintainers.pl does the
right thing and makes sure everybody gets CCd:

$ ./scripts/get_maintainer.pl -f kernel/sched/psi.c
Johannes Weiner <[email protected]> (maintainer:PRESSURE STALL INFORMATION (PSI))
Ingo Molnar <[email protected]> (maintainer:SCHEDULER)
Peter Zijlstra <[email protected]> (maintainer:SCHEDULER)
...

Reported-by: Ivan Babrou <[email protected]>
Signed-off-by: Johannes Weiner <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]

Author: hnaz

MAINTAINERS

@@ -13518,6 +13518,12 @@ F:	net/psample
 F:	include/net/psample.h
 F:	include/uapi/linux/psample.h
 
+PRESSURE STALL INFORMATION (PSI)
+M:	Johannes Weiner <[email protected]>
+S:	Maintained
+F:	kernel/sched/psi.c
+F:	include/linux/psi*
+
 PSTORE FILESYSTEM
 M:	Kees Cook <[email protected]>
 M:	Anton Vorontsov <[email protected]>