Add comments per peer review

Author: kaleb-himes

wolfssl/wolfcrypt/settings.h

@@ -297,6 +297,10 @@
     #if FIPS_VERSION_LT(2,0)
         #define WC_RNG RNG
     #else
+        /* RNG needs to be defined to WC_RNG anytime another library on the
+         * system or other set of headers included by wolfSSL already defines
+         * RNG. Examples are:
+         * wolfEngine, wolfProvider and potentially other use-cases */
         #ifndef RNG
             #define RNG WC_RNG
         #endif