dma-buf: Improve CONFIG_DMABUF_MOVE_NOTIFY help text

Improve the help text for the CONFIG_DMABUF_MOVE_NOTIFY symbol by:
  1. Removing duplicated single quotes,
  2. Adding a missing subject,
  3. Fixing a misspelling of "yet",
  4. Wrapping long lines.

Fixes: bb42df46 ("dma-buf: add dynamic DMA-buf handling v15")
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200324125442.21983-1-geert+renesas@glider.be