fbdev: uvesafb: fix spelling mistake "memoery" -> "memory"

There is a spelling mistake in the module parameter description, fix it.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Cc: Michal Januszewski <spock@gentoo.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>