fix various typos

Saw a couple of typos fixes in the patch DragonFlyBSD carries [1], so
I ran codespell (a spell checker for code) on the whole repo.

[1] https://github.com/DragonFlyBSD/DPorts/blob/master/graphics/libdrm/files/patch-xf86drm.c



Signed-off-by: Eric Engestrom <eric.engestrom@intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>