net: core: fix some kernel-doc markups

Some identifiers have different names between their prototypes
and the kernel-doc markup.

In the specific case of netif_subqueue_stopped(), keep the
current markup for __netif_subqueue_stopped(), adding a
new one for netif_subqueue_stopped().

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>