apm-emulation: hide an unused variable

apm-emulation: hide an unused variable

The driver_version variable is only used inside of an #ifdef block, which
leads to a W=1 warning:

drivers/char/apm-emulation.c:144:19: error: 'driver_version' defined but not used [-Werror=unused-const-variable=]

Move this into the function using it.

Fixes: 7726942fb15e ("[APM] Add shared version of APM emulation")
Acked-by: Jiri Kosina <jkosina@suse.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20250409122314.2848028-9-arnd@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>