dma-buf: Fix kerneldoc of dma_buf_set_name()

Fix W=1 compile warnings (invalid kerneldoc):

    drivers/dma-buf/dma-buf.c:328: warning: Function parameter or member 'dmabuf' not described in 'dma_buf_set_name'

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200819175134.19261-1-krzk@kernel.org