net: phy: Add the missing blank line in the phylink_suspend comment

Fix warning as:

Documentation/networking/kapi:147: ./drivers/net/phy/phylink.c:1657: WARNING: Unexpected indentation.
Documentation/networking/kapi:147: ./drivers/net/phy/phylink.c:1658: WARNING: Block quote ends without a blank line; unexpected unindent.

Signed-off-by: Yanteng Si <siyanteng@loongson.cn>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>