Fix algorithm_auth and SSL_k* mismatch.

Fixes bug introduced in c26c802a8912a813181ea677b7da38d1d3aedcf8. Only one of
the two halves got flipped.

Change-Id: I0b3905ab22b0f83f093e1720af85594b1a970a7f
Reviewed-on: https://boringssl-review.googlesource.com/1152
Reviewed-by: Adam Langley <agl@google.com>