hwmon: (hp-wmi-sensors) fix debugfs check

hwmon: (hp-wmi-sensors) fix debugfs check

Checking for Kconfig symbols with #if is wrong:

drivers/hwmon/hp-wmi-sensors.c:1141:5: error: "CONFIG_DEBUG_FS" is not defined, evaluates to 0 [-Werror=undef]

This could be an #ifdef, but an IS_ENABLED() check is even better to
give the best compile coverage.

Fixes: 23902f98f8d4 ("hwmon: add HP WMI Sensors driver")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: James Seo <james@equiv.tech>
Link: https://lore.kernel.org/r/20230601213216.3220550-1-arnd@kernel.org
Signed-off-by: Guenter Roeck <linux@roeck-us.net>