drm/xe/vm_doc: Fix some typos

Fix some typos and add / remove / change a few words to improve
readability and prevent some ambiguities.

Signed-off-by: Francois Dugast <francois.dugast@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240506202950.109750-1-francois.dugast@intel.com
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>