net: phy: Convert to use sysfs_emit() APIs

Follow the advice of the Documentation/filesystems/sysfs.rst and show()
should only use sysfs_emit() or sysfs_emit_at() when formatting the value
to be returned to user space.

Signed-off-by: Wang Yufen <wangyufen@huawei.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/1664364860-29153-1-git-send-email-wangyufen@huawei.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>