PCI/PME: Make explicitly non-modular

This code is not being built as a module by anyone:

  config PCIE_PME
        def_bool y
        depends on PCIEPORTBUS && PM

Remove traces of modularity so that when reading the driver there is no
doubt it is builtin-only.

Also delete the .remove function, since that doesn't seem to have a
sensible use case.  With "normal" endpoint drivers, we have in the past set
the suppress_bind_attrs bit to make it clear that the use of ".remove" in a
builtin driver was deleted, but here for PCI, it seems overkill to jump
through the pcie_port_service_driver and into the struct device_driver in
order to finally try and do something similar with the bind setting.

Note that for non-modular code, module_init() translates to
device_initcall().

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