This patch allows to disable the serial port directly from Kconfig. This used
to only be possible from the command-line (by passing "uart=disabled"). To
disable the serial port via Kconfig, simply unselect the "Serial IO type"
option.
The default options do not seem to have any effect anymore (and were confusing
anyway) so they are removed and the serial port is enabled for various platforms
in their corresponding *.config file.
Tracked-On: #1481
Signed-off-by: Geoffroy Van Cutsem <geoffroy.vancutsem@intel.com>
26dc54ce37