gryphon-led-module: use the right toolchain on Broadcom targets
Userspace toolchain was being used to build the kernel module which although not correct happened to work on 32-bit kernel but obviously does not work on 64-bit kernel with 32-bit userspace.
Ideally, it should but enough to set KERNEL_CROSS if Build/Compile is updated to use KERNEL_CROSS instead of TARGET_CROSS, but not changing TARGET_CROSS breaks scripts/strip-kmod.sh which for some reason uses TARGET_CROSS rather than KERNEL_CROSS.