pcnet32: fix warning

pci_name() will be changed to return `const char *':

drivers/net/pcnet32.c: In function 'pcnet32_probe1':
drivers/net/pcnet32.c:1884: warning: passing argument 2 of 'pcnet32_alloc_ring' discards qualifiers from pointer target type

Cc: Jeff Garzik <jeff@garzik.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>