style: code refactoring

src/core/apu/Noise.zig

@@ -1,4 +1,5 @@
 const io = @import("../bus/io.zig");
+const util = @import("../../util.zig");
 
 const Scheduler = @import("../scheduler.zig").Scheduler;
 const FrameSequencer = @import("../apu.zig").FrameSequencer;
@@ -123,7 +124,7 @@ pub fn setNr44(self: *Self, fs: *const FrameSequencer, byte: u8) void {
         self.enabled = self.isDacEnabled();
     }
 
-    self.lfsr.updateLength(fs, self, new);
+    util.audio.length.ch4.update(self, fs, new);
     self.cnt = new;
 }
 
@@ -135,10 +136,6 @@ pub fn channelTimerOverflow(self: *Self, late: u64) void {
     self.sample = if (self.enabled) self.lfsr.sample() * @as(i8, self.env_dev.vol) else 0;
 }
 
-pub fn amplitude(self: *const Self) i16 {
-    return @as(i16, self.sample);
-}
-
 fn isDacEnabled(self: *const Self) bool {
     return self.envelope.raw & 0xF8 != 0x00;
 }