iwlwifi: hide kernel option IWLWIFI_DEVICE_SVTOOL

Because the testmode support should be the mandatory foundation
of test functionality, it is better to set kernel option
IWLWIFI_DEVICE_SVTOOL automatically instead of user configuration.

Signed-off-by: Kenny Hsu <kenny.hsu@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>