PCI: make pci_register_driver() a macro

alpha:

CC [M]  drivers/usb/gadget/u_ether.o
In file included from include/asm/dma-mapping.h:7,
                 from include/linux/dma-mapping.h:52,
                 from include/linux/dmaengine.h:29,
                 from include/linux/skbuff.h:29,
                 from include/linux/if_ether.h:114,
                 from include/linux/etherdevice.h:27,
                 from drivers/usb/gadget/u_ether.c:29:
include/linux/pci.h: In function 'pci_register_driver':
include/linux/pci.h:673: error: 'KBUILD_MODNAME' undeclared (first use in this function)
include/linux/pci.h:673: error: (Each undeclared identifier is reported only once
include/linux/pci.h:673: error: for each function it appears in.)

Sam says:

The problem is that u_ether.o is used by two modules so when we build it
KBUILD_MODNAME is not defined because kbuild does not know what value to
use.

And in pci.h we have the following inline:

static inline int __must_check pci_register_driver(struct pci_driver *driver)
{
        return __pci_register_driver(driver, THIS_MODULE, KBUILD_MODNAME);
}

And alpha uses dma-mapping.h to nullify a number of functions that seem to
require something from pci.h.

Making it a macro fixes this particular problem.  However, the underlying issue
of a file using KBUILD_MODNAME and being shared between multiple modules is
*not* addressed.  I guess the answer there is "don't do that".

Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>