net: page_pool: add page_pool_get()

net: page_pool: add page_pool_get()

There is a page_pool_put() function but no get equivalent.
Having multiple references to a page pool is quite useful.
It avoids branching in create / destroy paths in drivers
which support memory providers.

Use the new helper in bnxt.

Acked-by: Jesper Dangaard Brouer <hawk@kernel.org>
Reviewed-by: Dragos Tatulea <dtatulea@nvidia.com>
Reviewed-by: Mina Almasry <almasrymina@google.com>
Link: https://patch.msgid.link/20250820025704.166248-2-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>