[mlir][vulkan-runner] Use aligned pointer for host buffer

Fix incorrect pointer usage in Vulkan buffer and Memref descriptor binding:
- Vulkan runtime produced incorrect result if there is alignment.
- There was illegal memory access if binding a LLVM global materialized
  from a constant op (0xdeadbeef).

Reviewed By: antiagainst

Differential Revision: https://reviews.llvm.org/D132291