amr64: dts: librem5: disable auto DPDM

The bq25892 shares the USB 2 DP/DM with the dwc3 disable the auto negotiation
so there is no contention.

Signed-off-by: Angus Ainslie <angus@akkea.ca>
2 jobs for auto-dpdm in 71 minutes and 54 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #304726
librem5
build:aarch64

00:17:47

passed #304727
librem5:arm64
build:deb

01:11:54