quark_se: Don't enable UART 0 always

The defconfigs would always create a device for UART 0, which is
problematic in circumstances where both the x86 and ARC cores are
alive and one wants to use it in a non-default configuration.

Specifically: on Arduino 101 this is the bluetooth device and it
operates at 1MBps instead of of 115200kbps.  If an x86 app sets this
up correctly, but then starts the ARC core running an app which
doesn't reference this UART at all, the device will still exist and
set up the (wrong!) configuration, clobbering the correct settings.

Just remove the "def-bool y" bits from the defconfig.  There's no
need, users of these devices (e.g. the console) will enable them
anyway.  There's no value to compiling it in without a configured
user.

Issue: ZEP-1677
Change-Id: I4a0e944f23705495433e9f3d0459065f131579cb
Signed-off-by: Andy Ross <andrew.j.ross@intel.com>