Add default switch cases.

Bug 15387371

Change-Id: I97644bfd9dbdc1109630199bc897f8b2572d5e83
Reviewed-on: https://swiftshader-review.googlesource.com/4502
Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>
Tested-by: Nicolas Capens <capn@google.com>

src/Shader/PixelRoutine.cpp

diff --git a/src/Shader/PixelRoutine.cpp b/src/Shader/PixelRoutine.cpp
index c313eb4..c87f3cb 100644
--- a/src/Shader/PixelRoutine.cpp
+++ b/src/Shader/PixelRoutine.cpp
@@ -1400,6 +1400,8 @@
 				current.z = current.z - As<Short4>(As<UShort4>(current.z) >> 8) + Short4(0x0080, 0x0080, 0x0080, 0x0080);
 				current.w = current.w - As<Short4>(As<UShort4>(current.w) >> 8) + Short4(0x0080, 0x0080, 0x0080, 0x0080);
 				break;
+			default:
+				break;
 			}
 		}