Multisampled blitter clear fix
Multisampled blitter clear fix

When clearing a multisampled buffer, the reactor blitter was only
clearing the first sample. This cl makes the reactor blitter
effectively clear all samples of a multisampled buffer.

Change-Id: I7ce1af401bf537fe85e1c8393a2c57144641ad8e
Reviewed-on: https://swiftshader-review.googlesource.com/18032
Tested-by: Alexis Hétu <1c7141772178a7e80858c3db5052b328076f08f4@google.com>
Reviewed-by: Nicolas Capens <51edc787c30f24c4904e8ffbb5523c3a9f7a451d@google.com>

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