Fixes for configure used in wolfssl-examples/signature/rsa_vfy_only and fix...

Fixes for configure used in wolfssl-examples/signature/rsa_vfy_only and fix for wrong WOLFSSL_MP_PUBLIC defines.
./configure CFLAGS=-DWOLFSSL_PUBLIC_MP --disable-asn --disable-filesystem --enable-static --enable-shared --enable-cryptonly --enable-sp=smallrsa2048 --enable-sp-math --disable-dh --disable-ecc --disable-sha224 --enable-rsavfy