nak: fix clippy::single_match warnings

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27234>

src/nouveau/compiler/nak/assign_regs.rs

@@ -1202,12 +1202,9 @@ impl Shader {
                 live = SimpleLiveness::for_function(f);
                 max_live = live.calc_max_live(f);
 
-                match file {
-                    RegFile::Bar => {
+                if file == RegFile::Bar {
                     tmp_gprs = max(tmp_gprs, 2);
                 }
-                    _ => (),
-                }
             }
         }
 

src/nouveau/compiler/nak/encode_sm70.rs

@@ -2088,14 +2088,11 @@ impl Shader {
         for b in &func.blocks {
             labels.insert(b.label, ip);
             for instr in &b.instrs {
-                match &instr.op {
-                    Op::Nop(op) => {
+                if let Op::Nop(op) = &instr.op {
                     if let Some(label) = op.label {
                         labels.insert(label, ip);
                     }
                 }
-                    _ => (),
-                }
                 ip += 4;
             }
         }