of: unittest: Fix of_unittest_pci_node() kconfig dependencies

of: unittest: Fix of_unittest_pci_node() kconfig dependencies

of_unittest_pci_node test depends on both CONFIG_PCI_DYNAMIC_OF_NODES
and CONFIG_OF_OVERLAY. Move the test into the existing
CONFIG_OF_OVERLAY ifdef and rework the CONFIG_PCI_DYNAMIC_OF_NODES
dependency to use IS_ENABLED() instead. This reduces the combinations to
build.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202308241954.oRNfVqmB-lkp@intel.com/
Fixes: 26409dd04589 ("of: unittest: Add pci_dt_testdrv pci driver")
Cc: Lizhi Hou <lizhi.hou@amd.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20230824221743.1581707-1-robh@kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>