Add more comment for wpa_supplicant using soong

This CL add 2 main section:
1. Point out the scope for 2 different products, one is cuttlefish and
   the other is non-cuttlefish(ex: pixel or other oems').
2. Example for adding product configuration to work using soong.

Bug: 359745733
Test: m hostapd_cli hostapd libhostapd_aidl wpa_cli wpa_supplicant \
        wpa_supplicant_macsec libwpa_client libwpa_aidl libpasn
Change-Id: I62cdaa30e5b9176701a74fea2c2c8ac6eacec09f
2 files changed