ARM: davinci: Fix trivial spelling

The word 'descriptor' is misspelled throughout the tree.

Fix it up accordingly:
    decriptors -> descriptors

Reviewed-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
[nsekhar@ti.com: fixed up subject prefix]
Signed-off-by: Sekhar Nori <nsekhar@ti.com>