MAINTAINERS: Add a missing entry for the NVDIMM device

Signed-off-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: NThomas Huth <thuth@redhat.com>
Message-Id: <20181125205000.10324-22-philmd@redhat.com>
Signed-off-by: NLaurent Vivier <laurent@vivier.eu>

MAINTAINERS

@@ -1498,6 +1498,7 @@ S: Maintained
 F: hw/acpi/nvdimm.c
 F: hw/mem/nvdimm.c
 F: include/hw/mem/nvdimm.h
+F: docs/nvdimm.txt
 
 e1000x
 M: Dmitry Fleytman <dmitry.fleytman@gmail.com>