ARM: dts: omap5-uevm: Remove pinmux for dmic pins

When the omap5-evm.dts file has been renamed to omap5-uevm.dts and the sEVM
support got deprecated in favor of uEVM (or Panda5) the content was not
validated.
Panda5 does not have support for digital microphones so remove the pinmux
section for it.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Benoit Cousson <bcousson@baylibre.com>