Fix R8_SNORM implementation format.

Change-Id: I68d7dbb445eee85e8a2ff4ac3a6fc6b31c6ea305
Reviewed-on: https://swiftshader-review.googlesource.com/15369
Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
diff --git a/src/OpenGL/common/Image.cpp b/src/OpenGL/common/Image.cpp
index 3336c67..a56f8b7 100644
--- a/src/OpenGL/common/Image.cpp
+++ b/src/OpenGL/common/Image.cpp
@@ -758,6 +758,7 @@
 			case GL_LUMINANCE8_ALPHA8_EXT:
 				return sw::FORMAT_A8L8;
 			case GL_R8_SNORM:
+				return sw::FORMAT_R8_SNORM;
 			case GL_R8:
 			case GL_RED:
 				return sw::FORMAT_R8;