Fix support for all GL_EXT_read_format_bgra formats.
Fix support for all GL_EXT_read_format_bgra formats.

Change-Id: I9b3977959aea8bd2711ebd94e06c0e09376d4d6e
Reviewed-on: https://swiftshader-review.googlesource.com/4768
Tested-by: Nicolas Capens <0612353e1fcebbfd4b302d9337447ca0cdfa9122@google.com>
Reviewed-by: Alexis Hétu <1c7141772178a7e80858c3db5052b328076f08f4@google.com>
Reviewed-by: Nicolas Capens <0612353e1fcebbfd4b302d9337447ca0cdfa9122@google.com>

google/swiftshader,bkaradzic/SwiftShader,google/swiftshader,bkaradzic/SwiftShader,bkaradzic/SwiftShader,bkaradzic/SwiftShader,google/swiftshader,bkaradzic/SwiftShader