sh_eth: replace devm_kzalloc() with devm_kmalloc_array()

When I was converting the driver to the managed device API, only devm_kzalloc()
was available for memory allocation, so I had to use it, despite zeroing out the
PHY IRQ array right before initializing all  its entries to PHY_POLL was quite
stupid.   Now that devm_kmalloc_array() has become available, we can avoid the
needless zeroing out...

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: David S. Miller <davem@davemloft.net>