init: Add support for kernels that don't have finit_module

Some kernels don't have finit_module, which makes booting Android 7.0
impossible if people can't backport it themselves, so set 
KERNEL_HAS_FINIT_MODULE := false in BoardConfig.mk file to
allow booting 7.0 even when the kernel doesn't have finit_
module :)

Change-Id: Iec63c1846cdc5e5bb3b61610ea438cf8eff8635b