[PKTGEN]: Deinitialise static variables.

static variables should not be explicitly initialised to 0.  This causes
them to be placed in .data instead of .bss.  This patch de-initialises 3
static variables in net/core/pktgen.c.

There are approximately 800 more such variables in the source tree
(2.6.15rc5).  If there is more interrest I'd be willing to track down the
rest of these as well and de-initialise them as well.

Signed-off-by: David S. Miller <davem@davemloft.net>