reset-gpios is more clear than rst-gpio.

This change has been done as one atomic commit but it
does breaks compatability with older dtbs.
Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
Acked-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>