R600/SI: Fix extra whitespace in asm str

This slipped in in r214467, so something like

V_MOV_B32_e32  v0, ... is now printed with 2 spaces
between the instruction name and first operand.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214660 91177308-0d34-0410-b5e6-96231b3b80d8