[PATCH] PNP: export pnp_bus_type

The PNP framework doesn't export "pnp_bus_type", which is an unfortunate
exception to the policy followed by pretty much every other bus.  I noticed
this when I had to find a device in order to provide its platform_data.

Note that per advice from Arjan, the "export" scope has been been minimized to
avoid the hundred-plus bytes needed to support access from modules.  In this
case, the symbol is only needed by statically linked kernel code that lives
outside the drivers/pnp directory.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: Adam Belay <ambx1@neo.rr.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>