MAINTAINERS: Add file patterns for perf device tree bindings

Submitters of device tree binding documentation may forget to CC
the subsystem maintainer if this is missing.
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Will Deacon <will.deacon@arm.com>

MAINTAINERS

@@ -976,6 +976,7 @@ F:	arch/arm*/include/asm/perf_event.h
 F:	drivers/perf/*
 F:	include/linux/perf/arm_pmu.h
 F:	Documentation/devicetree/bindings/arm/pmu.txt
+F:	Documentation/devicetree/bindings/perf/
 
 ARM PORT
 M:	Russell King <linux@armlinux.org.uk>