ARM: dts: at91: sam9x60: fix the ddr clock for sam9x60

The 2nd DDR clock for sam9x60 DDR controller is peripheral clock with
id 49.

Fixes: 1e5f532c

 ("ARM: dts: at91: sam9x60: add device tree for soc and board")
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20221208115241.36312-1-claudiu.beznea@microchip.com