PNP: make pnpbios core explicitly non-modular

The Kconfig currently controlling compilation of this code is:

config PNPBIOS
        bool "Plug and Play BIOS support"

...meaning that it currently is not being built as a module by anyone.

Lets remove the couple traces of modularity, so that when reading the
driver there is no doubt it is builtin-only.

Since module_init translates to device_initcall in the non-modular
case, the init ordering remains unchanged with this commit.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>