net: vxge: Remove unused device pointer

Remove occurrences of unused struct __vxge_hw_device pointer in functions
vxge_learn_mac() and vxge_rem_isr().

Detected by Coverity: CID 139839, CID 139842.

Signed-off-by: Christian Engelmayer <cengelma@gmx.at>
Reviewed-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: David S. Miller <davem@davemloft.net>