drm/uapi: drm_mode.h: fix spellos and grammar

Correct spellos reported by codespell.
Fix some grammar (as 's' to a few words).

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: David Airlie <airlied@gmail.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Maxime Ripard <mripard@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20231213044107.29214-1-rdunlap@infradead.org