net: phy: Remove unnecessary indentation in the comments of phy_device

Fix warning as:

linux-next/Documentation/networking/kapi:122: ./include/linux/phy.h:543: WARNING: Unexpected indentation.
linux-next/Documentation/networking/kapi:122: ./include/linux/phy.h:544: WARNING: Block quote ends without a blank line; unexpected unindent.
linux-next/Documentation/networking/kapi:122: ./include/linux/phy.h:546: WARNING: Unexpected indentation.

Suggested-by: Akira Yokosawa <akiyks@gmail.com>
Signed-off-by: Yanteng Si <siyanteng@loongson.cn>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>