atomic* value is signed value, and atomic* functions need also process
signed value (parameter value, and return value), so use 'long long'
instead of 'u64'.

After replacement, it will also fix a bug for atomic64_add_negative():
"u64 is never less than 0".

The modifications are:

  in vim, use "1,% s/\<u64\>/long long/g" command.
  remove redundant '__aligned(8)'.
  be sure of 80 (and macro '\') columns limitation after replacement.
Signed-off-by: Chen Gang <gang.chen@asianux.com>
Signed-off-by: Chris Metcalf <cmetcalf@tilera.com> [re-instated const cast]