Explicit cast uint64_t as unsigned long type

This fixes build errors caused by the difference in uint64_t
definitions between targets.

Bug: 149647375
Test: build for x86 target
Change-Id: I3a0845b0527a7cf0f20c7983870c2d3dd8219444
Signed-off-by: Changyeon Jo <changyeon@google.com>