gv100/ir: Initialize CodeEmitterGV100 members in constructor.

Fix defects reported by Coverity Scan.

uninit_member: Non-static class member prog is not initialized in this constructor nor in any functions that it calls.
uninit_member: Non-static class member insn is not initialized in this constructor nor in any functions that it calls.

Signed-off-by: Vinson Lee <vlee@freedesktop.org>
Reviewed-by: Karol Herbst <kherbst@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9183>

src/gallium/drivers/nouveau/codegen/nv50_ir_emit_gv100.cpp

@@ -2053,7 +2053,7 @@ CodeEmitterGV100::prepareEmission(Program *prog)
 }
 
 CodeEmitterGV100::CodeEmitterGV100(TargetGV100 *target)
-   : CodeEmitter(target), targ(target)
+   : CodeEmitter(target), prog(NULL), targ(target), insn(NULL)
 {
    code = NULL;
    codeSize = codeSizeLimit = 0;