1) hardcoded 1000000000 value is used five times in places where NSEC_PER_SEC 
might be more readable.

2) A conversion from nsec to msec uses the hardcoded 1000000 value, which is a 
candidate for NSEC_PER_MSEC.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>