ARM: at91: remove unnecessary of_platform_default_populate calls

The DT core will call of_platform_default_populate, so it is not
necessary for machine specific code to call it unless there are custom
match entries, auxdata or parent device. Neither of those apply here, so
remove the call.

Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Tested-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://lore.kernel.org/r/20260105-at91-probe-v3-3-594013ff2965@kernel.org
Signed-off-by: Claudiu Beznea <claudiu.beznea@tuxon.dev>