PCI: Add builtin_pci_driver() to avoid registration boilerplate

In f309d444

 ("platform_device: better support builtin boilerplate
avoidance"), we introduced the builtin_driver() macro.

Here we use that support and extend it to PCI driver registration, so where
a driver is clearly non-modular and builtin-only, we can register it in a
similar fashion.  Existing code that is clearly non-modular can be updated
with the simple mapping of

  module_pci_driver(...)  ---> builtin_pci_driver(...)

We've essentially cloned the former to make the latter, and taken out the
remove/module_exit parts since those never get used in a non-modular build
of the code.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>