Android recently split vulkan_headers (vulkan.h etc) from
hwvulkan_headers (HAL module plumbing, etc). Adjust to match.

Change-Id: I912cfa900363307abb271f74d9c8ebc683cada42
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/29772
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Tested-by: Chris Forbes <chrisforbes@google.com>