drm/i915/selftests: fix spelling mistake: "parmaters" -> "parameters"

Trivial fix to spelling mistake in pr_err error message

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/20180503154510.708-1-colin.king@canonical.com