rust: pci: do not depend on CONFIG_PCI_MSI

The PCI abstractions do not actually depend on CONFIG_PCI_MSI; it also
breaks drivers that only depend on CONFIG_PCI, hence drop it.

While at it, move the module entry to its correct location.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202501030744.4ucqC1cB-lkp@intel.com/


Fixes: 3a9c0919 ("rust: pci: add basic PCI device / driver abstractions")
Signed-off-by: Danilo Krummrich <dakr@kernel.org>