net: clear heap allocation for ethtool_get_regs()

There is a conflict between commit b00916b1 and a77f5db3. This patch resolves
the conflict by clearing the heap allocation in ethtool_get_regs().

Cc: stable@kernel.org
Signed-off-by: Eugene Teo <eugeneteo@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>