linux: disable UEVENT_HELPER by default on versions >= 3.15

+3
+3
pkgs/os-specific/linux/kernel/common-config.nix
··· 310 310 SLIP_COMPRESSED y # CSLIP compressed headers 311 311 SLIP_SMART y 312 312 THERMAL_HWMON y # Hardware monitoring support 313 + ${optionalString (versionAtLeast version "3.15") '' 314 + UEVENT_HELPER n 315 + ''} 313 316 ${optionalString (versionOlder version "3.15") '' 314 317 USB_DEBUG? n 315 318 ''}