net/core/pktgen.c: Use pr_<level>

Add pr_fmt(fmt) KBUILD_MODNAME ": " fmt
Remove "pktgen: " from formats
Convert printks to pr_<level>
Added func_enter() for debugging
Moved version to end of string at module_init
Coalesced long formats
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: David S. Miller <davem@davemloft.net>