sh_eth: re-enable-E-MAC interrupts in sh_eth_set_ringparam()

The E-MAC interrupts are left disabled when the ring parameters are changed
via 'ethtool'. In order to fix this, it's enough to call sh_eth_dev_init()
with 'true' instead of 'false' for the second argument (which conveniently
allows us to remove the following code re-enabling E-DMAC interrupts and
reception).

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