dts: Convert CONFIG_ to DT_ symbols for chosen props

Replace generating CONFIG_ symbols with DT_ symbols for chosen
properties like 'zephyr,console' or 'zephyr,bt-mon-uart'.  We now use a
kconfigfunctions (dt_str_val) to extract the info from dts into Kconfig.

Signed-off-by: Kumar Gala <kumar.gala@linaro.org>
6 files changed