r600/sfn: Initialize TestShaderFromString member m_instr_factory.
Fix defect reported by Coverity Scan.
Uninitialized pointer field (UNINIT_CTOR) uninit_member: Non-static class member m_instr_factory is not initialized in this constructor nor in any functions that it calls.
Fixes: 79ca456b ("r600/sfn: rewrite NIR backend") Signed-off-by: Vinson Lee vlee@freedesktop.org