PNPBIOS: remove include/linux/pnpbios.h

The contents of include/linux/pnpbios.h are used only inside the PNPBIOS
backend, so this file doesn't need to be visible outside PNP.

This patch moves the contents into an existing PNPBIOS-specific file,
drivers/pnp/pnpbios/pnpbios.h.

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Acked-By: Rene Herman <rene.herman@gmail.com>
Signed-off-by: Len Brown <len.brown@intel.com>