[AMDGPU][MC] Fix GFX12 check line typo and move test

NFC.
Fix CHECK lines that seem to have a copy paste error.
Move the test that was formerly in gfx12_dasm_vinterp.txt (see #85949).

Author: Sisyph

llvm/test/MC/Disassembler/AMDGPU/gfx12_dasm_features.txt

@@ -12,8 +12,13 @@
 # GFX12: v_add3_u32_e64_dpp v5, v1, 42, v0 dpp8:[7,6,5,4,3,2,1,0] ; encoding: [0x05,0x00,0x55,0xd6,0xe9,0x54,0x01,0x04,0x01,0x77,0x39,0x05]
 0x05,0x00,0x55,0xd6,0xe9,0x54,0x01,0x04,0x01,0x77,0x39,0x05
 
-# GFX1150: v_add3_u32_e64_dpp v5, v1, s2, s3 dpp8:[7,6,5,4,3,2,1,0] ; encoding: [0x05,0x00,0x55,0xd6,0xe9,0x04,0x0c,0x00,0x01,0x77,0x39,0x05]
+# GFX12: v_add3_u32_e64_dpp v5, v1, s2, s3 dpp8:[7,6,5,4,3,2,1,0] ; encoding: [0x05,0x00,0x55,0xd6,0xe9,0x04,0x0c,0x00,0x01,0x77,0x39,0x05]
 0x05,0x00,0x55,0xd6,0xe9,0x04,0x0c,0x00,0x01,0x77,0x39,0x05
 
-# GFX1150: v_cmp_ne_i32_e64_dpp vcc_lo, v1, s2 dpp8:[7,6,5,4,3,2,1,0] ; encoding: [0x6a,0x00,0x45,0xd4,0xe9,0x04,0x00,0x00,0x01,0x77,0x39,0x05]
+# GFX12: v_cmp_ne_i32_e64_dpp vcc_lo, v1, s2 dpp8:[7,6,5,4,3,2,1,0] ; encoding: [0x6a,0x00,0x45,0xd4,0xe9,0x04,0x00,0x00,0x01,0x77,0x39,0x05]
 0x6a,0x00,0x45,0xd4,0xe9,0x04,0x00,0x00,0x01,0x77,0x39,0x05
+
+# Check that unused bits in the encoding are ignored.
+# This is more strict than the check in vinterp-fake16.txt and is GFX12 specific.
+# GFX12: v_interp_p10_f32 v0, v1, v2, v3 wait_exp:0 ; encoding: [0x00,0x00,0x00,0xcd,0x01,0x05,0x0e,0x04]
+0x00,0x00,0xe0,0xcd,0x01,0x05,0x0e,0x1c