Restore use of midrange simd implementation

In fe6e73b5, Zack created two macros: HAVE_SIMD_CHACHA, and
HAVE_SIMD_CHACHA_2.  That's well and good, but two files looked for
HAVE_SIMD_CHACHA_1 instead of HAVE_SIMD_CHACHA.  Fixed those.

Found while investigating why simd1 had no coverage.