net: netdevsim: select PAGE_POOL in Kconfig

build bot points out that I forgot to add the PAGE_POOL
config dependency when adding the support in netdevsim.

Fixes: 1580cbcb ("net: netdevsim: add some fake page pool use")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202404170348.thxrboF1-lkp@intel.com/
Closes: https://lore.kernel.org/oe-kbuild-all/202404170527.LIAPSyMB-lkp@intel.com/
Link: https://lore.kernel.org/r/20240416232137.2022058-1-kuba@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>