nvc0/ir: Initialize NVC0LoweringPass member gpEmitAddress.

Fix defect reported by Coverity Scan.

Uninitialized pointer field (UNINIT_CTOR)
uninit_member: Non-static class member gpEmitAddress is not initialized
in this constructor nor in any functions that it calls.

Signed-off-by: Vinson Lee <vlee@freedesktop.org>
Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8605>

src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.cpp

@@ -883,7 +883,8 @@ NVC0LegalizePostRA::visit(BasicBlock *bb)
    return true;
 }
 
-NVC0LoweringPass::NVC0LoweringPass(Program *prog) : targ(prog->getTarget())
+NVC0LoweringPass::NVC0LoweringPass(Program *prog) : targ(prog->getTarget()),
+   gpEmitAddress(NULL)
 {
    bld.setProgram(prog);
 }