cryptfs: Fix encryption issue due to stack corruption.

Ioctl BLKGETSIZE expects pointer to unsigned long as argument.

On 64bit target using pointer to unsigned int can cause stack
corruption due to type mismatch.

props to https://github.com/aopp/android_system_vold/commit/f8b8787317fc94439b63bc891eeda83f7ae2f4f6

Change-Id: I1d76c65e29479c8f0cd44b6892069b21b8249b95