Revert "default-configs/: Delete the whole directory"

This reverts commit c8bfcd409b04a836335fee38b501244ec8d88ca0.

Signed-off-by: Ákos Kovács <akoskovacs@gmx.com>
Makefile: Make Kconfig configuration optional

configure: Append CONFIG_DEVICES_FILE=config-all-devices.mak to the config-host.mak
Use this new variable to control the current device configuration place.

If the user wants to configure QEMU with Kconfig, replace
config-all-devices.mak to kconfig-devices.mak at config-host.mak to
use the new configuration.

Make defconfig target capable to restore the original behaviour.

Signed-off-by: Ákos Kovács <akoskovacs@gmx.com>