video: fbdev: nvidia: fix spelling mistake: "scaleing" -> "scaling"

Trivial fix to spelling mistake in module parameter description text.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Cc: Antonino Daplas <adaplas@gmail.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>