Add channel 4 lfsr mode flip rom tests

Author: YushiOMOTE

README.md

@@ -114,6 +114,8 @@ Test status of [Same Suite](https://github.com/YushiOMOTE/SameSuite/tree/430ab7f
 * [x] `apu/div_trigger_volume_10.gb`
 * [x] `apu/channel_4/channel_4_lfsr.gb`
 * [x] `apu/channel_4/channel_4_lfsr15.gb`
+* [x] `apu/channel_4/channel_4_lfsr_7_15.gb`
+* [x] `apu/channel_4/channel_4_lfsr_15_7.gb`
 
 ## Projects
 

core/src/apu/noise.rs

@@ -126,6 +126,7 @@ impl Noise {
         }
 
         self.nr43 = Nr43::from_bits(value);
+        self.lfsr.set_mode(self.nr43.step());
     }
 
     /// Read NR44 register (0xff23)
@@ -277,6 +278,10 @@ impl Lfsr {
         self.value = 0xff;
     }
 
+    fn set_mode(&mut self, short: bool) {
+        self.short = short;
+    }
+
     fn update(&mut self) {
         // Xor bit 0 and 1.
         let bit = (self.value & 1) ^ ((self.value & 2) >> 1) & 1;