kconfig: boards: native_posix: Remove redundant BOARD_NATIVE_POSIX dep.
kconfig: boards: native_posix: Remove redundant BOARD_NATIVE_POSIX dep.

Appears within an 'if BOARD_NATIVE_POSIX' in the same file.

'if FOO' is just shorthand for adding 'depends on FOO' to each item
within the 'if'. Dependencies on menus work similarly. There are no
"conditional includes" in Kconfig, so 'if FOO' has no special meaning
around a source. Conditional includes wouldn't be possible, because an
if condition could include (directly or indirectly) forward references
to symbols not defined yet.

Tip: When adding a symbol, check its dependencies in the menuconfig
('ninja menuconfig', then / to jump to the symbol). The menuconfig also
shows how the file with the symbol got included, so if you see
duplicated dependencies, it's easy to hunt down where they come from.

Signed-off-by: Ulf Magnusson <01743f1c1deb1fe75271d62edb65757d98ac0bcb@nordicsemi.no>

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