x86/Kconfig: Fix an unused variable error in dell-smm-hwmon

When CONFIG_PROC_FS is not set, there is a build warning (turned
into an error):

  ../drivers/hwmon/dell-smm-hwmon.c: In function 'i8k_init_procfs':
  ../drivers/hwmon/dell-smm-hwmon.c:624:24: error: unused variable 'data' [-Werror=unused-variable]
    struct dell_smm_data *data = dev_get_drvdata(dev);

Make I8K depend on PROC_FS and HWMON (instead of selecting HWMON -- it
is strongly preferred to not select entire subsystems).

Build tested in all possible combinations of SENSORS_DELL_SMM, I8K, and
PROC_FS.

Fixes: 039ae58 ("hwmon: Allow to compile dell-smm-hwmon driver without /proc/i8k")
Reported-by: Arnd Bergmann <[email protected]>
Signed-off-by: Randy Dunlap <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Reviewed-by: Arnd Bergmann <[email protected]>
Acked-by: Guenter Roeck <[email protected]>
Acked-by: Pali Rohár <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]

Author: rddunlap

arch/x86/Kconfig

@@ -1256,7 +1256,8 @@ config TOSHIBA
 
 config I8K
 	tristate "Dell i8k legacy laptop support"
-	select HWMON
+	depends on HWMON
+	depends on PROC_FS
 	select SENSORS_DELL_SMM
 	help
 	  This option enables legacy /proc/i8k userspace interface in hwmon