Support GL_BGRA_EXT readback for all normalized formats.

Bug swiftshader:38

Change-Id: Ice466d96e4d71d546e5770551cc4188f8364edd0
Reviewed-on: https://swiftshader-review.googlesource.com/9029
Tested-by: Nicolas Capens <capn@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>

src/OpenGL/libGLESv2/utilities.cpp

diff --git a/src/OpenGL/libGLESv2/utilities.cpp b/src/OpenGL/libGLESv2/utilities.cpp
index f3c190d..8452dae 100644
--- a/src/OpenGL/libGLESv2/utilities.cpp
+++ b/src/OpenGL/libGLESv2/utilities.cpp
@@ -636,6 +636,17 @@
 			{
 				return true;
 			}
+
+			// GL_EXT_read_format_bgra combinations.
+			if(format == GL_BGRA_EXT)
+			{
+				if(type == GL_UNSIGNED_BYTE ||
+				   type == GL_UNSIGNED_SHORT_4_4_4_4_REV_EXT ||
+				   type == GL_UNSIGNED_SHORT_1_5_5_5_REV_EXT)
+				{
+					return true;
+				}
+			}
 		}
 		else if(sw::Surface::isFloatFormat(internalformat))
 		{