Build libwifi-hal-* modules only for the first arch

Previously, the build rules assumed that the target supports both 64 and
32 bit architectures, which isn't true for 32-bit-only targets. That
caused build breakage on such targets. Fixing that by building the
modules only for the first architecture (64 on 64-only or 64/32 target,
and 32 on 32-only target).

Bug: 241916304
Test: build the 32-bit-only target
Change-Id: I5353ab1561622eae12e2dff87eb0f17b47c3773d