libc: minimal: Add error codes for key management
libc: minimal: Add error codes for key management

This adds EKEY* codes, as defined by Linux, using the same numeric
values as Linux.

Signed-off-by: Nils Montenegro <5ef0953a16f081d174daeb1921534c3ff3cc8036@nordicsemi.no>

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