R600/SI: Use -verify-machineinstrs for most tests

We can't enable the verifier for tests with SI_IF and SI_ELSE, because
these instructions are always followed by a COPY which copies their
result to the next basic block.  This violates the machine verifier's
rule that non-terminators can not folow terminators.

Reviewed-by: Vincent Lejeune<vljn at ovi.com>
llvm-svn: 192366