board: purism: librem5: disable DPDM and ICO

Enabling these causes USB errors on the host and device side. On the L5 we see

SDP: initialize...
SDP: handle requests...
Status: -108
Status: -108
Status: -108

And on the host side there are messages about failing to negotiate and address.

Signed-off-by: Angus Ainslie <angus@akkea.ca>
1 job for status-108 in 2 minutes and 33 seconds (queued for 2 seconds)
Status Name Job ID Coverage
  Build
passed build:cross:debian-buster #377718
librem5

00:02:33