dma-buf: A collection of typo and documentation fixes

I've been collecting these typo fixes for a while and it feels like
time to send them in.

Signed-off-by: T.J. Mercier <tjmercier@google.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Tommaso Merciai <tommaso.merciai@amarulasolutions.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221123193519.3948105-1-tjmercier@google.com


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