Make sp_rshd not available when WOLFSSL_SP_MATH in header.
sp_rshd is not required by any wolfCrypt code.
Fix sp_rshd comment on #endif
Make sp_div publicly available in some WOLFSSL_SP_MATH builds.
Delare sp_div for some WOLFSSL_SP_MATH builds.
Fix test.c to compile with WOLFSL_SP_MATH and HAVE_VALGRIND.