[NET]: Fix dev_put() and dev_hold() comments

Trivial fix: Swap comments for dev_put() and dev_hold() to get them 
at the right place.
Typo introduced by 4fa57c9ea9f36f9ca852f3a88ca5d2f1aebbc960.

Signed-of-by: Benjamin Thery <benjamin.thery@bull.net>
Signed-off-by: David S. Miller <davem@davemloft.net>