Only skip _16k/_64k kernel modules dirs on 4K builds

The initramfs.img from kernel builds do not store kernel modules under
_16k directory. Currently, init is programmed to only load kernel
modules from _16k dir if running on 16K page size kernel. Relax this
restriction so that booting on custom 16K kernel would work without
going through platform rebuild.

Test: th
Bug: 293313353
Bug: 300184677

Change-Id: I9ee3c74066ad9ec5127f1e8662f7c1273445994c