ARM: at91/dt: sama5d3: use new pinctrl compatible string

This switches the SAMA5D3 to use the new atmel,sama5d3-pinctrl id that was
added with the drive strength options patch.

Signed-off-by: Marek Roszko <mark.roszko@gmail.com>
[nicolas.ferre@atmel.com: second compatible string kept as at91sam9x5]
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>