lib/fdtable: Can call zephyr_write() only for CONFIG_NEWLIB_LIBC
lib/fdtable: Can call zephyr_write() only for CONFIG_NEWLIB_LIBC

If we don't have Newlib, the more or less POSIX library, it's unclear
how to deal with POSIX stdin/stdout/stderr at all.

Signed-off-by: Paul Sokolovsky <35cb557f011771c94f127d6fef99f804b62203f5@linaro.org>

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