Fill buffer fix
Fill buffer fix

memset was erroneously being used to copy 4 bytes at a time,
but the integer input value in memset is used as an 8 bit value,
so the fill was failing if the 4 bytes were not identical.

Tests: dEQP-VK.api.fill_and_update_buffer.*
Tests: dEQP-VK.memory.pipeline_barrier.host_read_transfer_dst.*

Bug b/118383648

Change-Id: I29cb5915ebd3773b4afbd89850c47a042fff6952
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/27872
Reviewed-by: Nicolas Capens <51edc787c30f24c4904e8ffbb5523c3a9f7a451d@google.com>
Tested-by: Alexis Hétu <1c7141772178a7e80858c3db5052b328076f08f4@google.com>
Kokoro-Presubmit: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>

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