dma-buf: Add syntax highlighting to code listings in the document

dma-buf: Add syntax highlighting to code listings in the document

This patch tries to improve the display of the code listing
on The Linux Kernel documentation website for dma-buf [1] .

Originally, it appears that it was attempting to escape
the '*' character, but looks like it's not necessary (now),
so we are seeing something like '\*' on the webite.

This patch removes these unnecessary backslashes and adds syntax
highlighting to improve the readability of the code listing.

[1] https://docs.kernel.org/driver-api/dma-buf.html

Signed-off-by: Tommy Chiang <ototot@chromium.org>
Reviewed-by: T.J. Mercier <tjmercier@google.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240119033126.1802711-1-ototot@chromium.org
Signed-off-by: Christian König <christian.koenig@amd.com>