Increase the size of ring buffer's byte counters to avoid overflow

Fix overflow of ring buffer counters which count the total bytes
over time i.e. total_bytes_written, total_bytes_read and
total_bytes_overwritten by increasing their size from u32 to u64.

Change-Id: I77f0bc4cb3c88d02c1c370273c2fe7594f62f195
CRs-Fixed: 2456561