ARM: dts: at91: sama5d2_xplained: Remove pdmic node

The PDMIC needs PDM microphones to work. sama5d2 xplained doesn't have
such microphones, so there is no reason to enable PDMIC and take the
pins since there is no-one using them.

Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu@microchip.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20200618152845.682723-1-codrin.ciubotariu@microchip.com