mv643xx_eth: Neaten mv643xx_eth_program_multicast_filter

The code around the allocation and loops are a bit obfuscated.

Neaten it by using:

o kcalloc with decimal count and sizeof(u32)
o Decimal loop indexing and i++ not i += 4
o A promiscuous block using a similar style
  to the multicast block
o Remove unnecessary variables

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: David S. Miller <davem@davemloft.net>