LEDS: tca6507 - fix up some comments.

In particular fix the capitalisation of GPIO and LED and
correct TCA6507_MAKE_CPIO, but also rewrite the comment about
platform-data to include reference to devicetree.

Also re-wrap comments to fit 80 columns.

Reported-by: Bryan Wu <cooloney@gmail.com>
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Bryan Wu <cooloney@gmail.com>