Remove unused info_str parameter to pcnet_common_init()

Remove unused info_str parameter to pcnet_common_init()

I noticed that pcnet_common_init() takes an unused 'info_str'
parameter, added in r2142.  Since then, we always pass "pcnet"
to register_savevm() (and never "lance").

Note that r6218 changed vc->info_str to "lance" for sun4m emulation.

On the assumption that it's not needed, this patch removes the
parameter.  If reverting the change in r2142, and registering with
"lance" would be preferable, I can submit a patch to do so.

Signed-off-by: Stuart Brady <stuart.brady@gmail.com>
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6362 c046a42c-6fe2-441c-8c8c-71466251a162