net: sfp: Remove unused function declaration sfp_link_configure()

Commit ce0aa27f

 ("sfp: add sfp-bus to bridge between network devices and sfp cages")
declared but never implemented it.

Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>