nn: Ensure BlobCache entries are aligned by size_t

On most chromeos systems alignof(size_t) == 8. The current code was
assuming alignment of 4, which caused ubsan failures.

Reviewed-on: https://chromium-review.googlesource.com/c/aosp/platform/frameworks/ml/+/2299967
(cherry picked from commit b92c7b25802659cc1858867d007ea64ccbde67b1)

Bug: 161103287
Test: mma in frameworks/ml
      all tests from BlobCache_test pass on host x86 and x86_64
      all tests from BlobCache_test pass on device (blueline)

Change-Id: I37c5aa301988fe289fcbe3d33cfb7ae9d4b962ad
1 file changed