drm/i915/selftests: fix spelling mistake "submited" -> "submitted"

There is a spelling mistake in a pr_err message. Fix it.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20200617085207.167552-1-colin.king@canonical.com