MAINTAINERS: Add selftests to DMA-BUF HEAPS FRAMEWORK entry

Include dmabuf-heaps selftests in the correct entry so that updates to it
can be sent to the right place.

Signed-off-by: Zenghui Yu <[email protected]>
Signed-off-by: Daniel Vetter <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

Author: Zenghui Yu

MAINTAINERS

@@ -6530,6 +6530,7 @@ F:	drivers/dma-buf/dma-heap.c
 F:	drivers/dma-buf/heaps/*
 F:	include/linux/dma-heap.h
 F:	include/uapi/linux/dma-heap.h
+F:	tools/testing/selftests/dmabuf-heaps/
 
 DMC FREQUENCY DRIVER FOR SAMSUNG EXYNOS5422
 M:	Lukasz Luba <[email protected]>