dma-buf: Fix the typo in DMA-BUF statistics doc

The kernel-doc for DMA-BUF statistics mentions /sys/kernel/dma-buf/buffers
but the correct path is /sys/kernel/dmabuf/buffers instead.

Signed-off-by: Luc Ma <luc@sietium.com>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/64b6749a.170a0220.3acab.2af9@mx.google.com


Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Christian König <christian.koenig@amd.com>