A condition was overly aggressive in producing an INVALID_OPERATION
when the read depth/stencil framebuffer is multisampled. When the
formats are the same and source and destination rectangles are the
same, performing a blitFramebuffer operation is allowed.

Change-Id: I29e52cb546ae1bf248ac0107492c97ea82406613
Reviewed-on: https://swiftshader-review.googlesource.com/8212Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>