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 <[e-mail]>
Reviewed-by: Javier Martinez Canillas <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]
Reviewed-by: Christian König <[e-mail]>
Signed-off-by: Christian König <[e-mail]>

drivers/dma-buf/dma-buf-sysfs-stats.c

···
  * into their address space. This necessitated the creation of the DMA-BUF sysfs
  * statistics interface to provide per-buffer information on production systems.
  *
- * The interface at ``/sys/kernel/dma-buf/buffers`` exposes information about
+ * The interface at ``/sys/kernel/dmabuf/buffers`` exposes information about
  * every DMA-BUF when ``CONFIG_DMABUF_SYSFS_STATS`` is enabled.
  *
  * The following stats are exposed by the interface: