This change fixes the ASAN issue as described in b/133135427.

Reproduction case:
./build/vk-unittests --gtest_repeat=-1 --gtest_filter=ComputeParams/SwiftShaderVulkanBufferToBufferComputeTest.Memcpy/0

Bug: b/133127573
Bug: b/133135427
Bug: swiftshader:130
Change-Id: I06fbf10ab042160e8ca481f2afaa30d4f676dc75
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/31681
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Chris Forbes <chrisforbes@google.com>
Tested-by: Ben Clayton <bclayton@google.com>