dma-buf: Couple of documentation typo fixes

Fix a couple of typos: "as" -> "has" and "int" -> "in".

Signed-off-by: Gal Pressman <galpress@amazon.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200420074115.23931-1-galpress@amazon.com