R600/SI: Add pattern for zero-extending i1 to i32

Fixes opencl-example if_* tests with radeonsi.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=74469

Reviewed-by: Tom Stellard <thomas.stellard@amd.com>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200830 91177308-0d34-0410-b5e6-96231b3b80d8