smc911x: Fix multicast handling

smc911x_set_multicast_list fails to fill out the multicast hash table
correctly; Bit 1 was used rather than bit 5 to decide if the lower or
upper register should be used.

The function is at the same time cleaned up by calling ether_crc rather
than using it's own bit reversal table.

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>
Signed-off-by: Jeff Garzik <jeff@garzik.org>