hostap: Add build support for Zephyr

Only adds basic build support using Zephyr. Crypto support is disabled
till the MbedTLS integration is complete.

Signed-off-by: Sridhar Nuvusetty <sridhar.nuvusetty@nordicsemi.no>
Signed-off-by: Sachin Kulkarni <sachin.kulkarni@nordicsemi.no>
Signed-off-by: Ravi Dondaputi <ravi.dondaputi@nordicsemi.no>
Signed-off-by: Krishna T <krishna.t@nordicsemi.no>