net: veth: Page pool creation error handling for existing pools only

The failure handling procedure destroys page pools for all queues,
including those that haven't had their page pool created yet. this patch
introduces necessary adjustments to prevent potential risks and
inconsistency with the error handling behavior.

Fixes: 0ebab78c

 ("net: veth: add page_pool for page recycling")
Acked-by: Jesper Dangaard Brouer <hawk@kernel.org>
Signed-off-by: Liang Chen <liangchen.linux@gmail.com>
Link: https://lore.kernel.org/r/20230812023016.10553-1-liangchen.linux@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>