kconfig: Removed source "[...]mgmt/mcumgr/mgmt/port/zephyr/Kconfig"
kconfig: Removed source "[...]mgmt/mcumgr/mgmt/port/zephyr/Kconfig"

This Kconfig 'source' statement had no effect as it was referencing a
non-existing Kconfig file. It is not clear if the intention is to
include-if-exists, but I presume not.

Signed-off-by: Sebastian Bøe <edee888afd63e94916688495334700803eba20a0@nordicsemi.no>

ldts/zephyr,nashif/zephyr,Vudentz/zephyr,galak/zephyr,explora26/zephyr,ldts/zephyr,nashif/zephyr,Vudentz/zephyr,kraj/zephyr,galak/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,punitvara/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,zephyriot/zephyr,punitvara/zephyr,galak/zephyr,nashif/zephyr,explora26/zephyr,zephyrproject-rtos/zephyr,kraj/zephyr,mbolivar/zephyr,kraj/zephyr,nashif/zephyr,zephyriot/zephyr,finikorg/zephyr,finikorg/zephyr,kraj/zephyr,GiulianoFranchetto/zephyr,galak/zephyr,explora26/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,zephyriot/zephyr,mbolivar/zephyr,ldts/zephyr,punitvara/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,mbolivar/zephyr,Vudentz/zephyr,punitvara/zephyr,GiulianoFranchetto/zephyr,galak/zephyr,punitvara/zephyr,explora26/zephyr,kraj/zephyr,GiulianoFranchetto/zephyr,explora26/zephyr,finikorg/zephyr,mbolivar/zephyr,finikorg/zephyr,GiulianoFranchetto/zephyr,zephyriot/zephyr,zephyriot/zephyr,finikorg/zephyr,nashif/zephyr,mbolivar/zephyr,ldts/zephyr,ldts/zephyr