drivers: pnp: isapnp: proc.c: Remove unnecessary local variables

In the PNP code, there are two redundant local variables that can be
dropped.

This also fixes a coding style issue reported by checkpatch about an
assignment made under an if () statement.

Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Signed-off-by: Anupama K Patil <anupamakpatil123@gmail.com>
[ rjw: Subject and changelog edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>