Revert "Build support for 32-bit armv8-a"

This reverts commit 0daa78ee.

Reason for revert: Broke the build for some targets (including marlin and angler).

$ make cts
build/core/combo/TARGET_linux-arm.mk:43: kryo is armv8-a.
build/core/combo/TARGET_linux-arm.mk:45: TARGET_2ND_ARCH_VARIANT, armv7-a-neon, ignored! Use armv8-a instead.
[...]
cts/tests/tests/os/jni/android_os_cts_CpuInstructions.cpp:88:20: error: instruction requires: armv7 or earlier
    asm volatile ( "swp r0, r0, [%0]" : "+r"(ptr) : : "r0" );
                   ^
<inline asm>:1:2: note: instantiated into assembly here
        swp r0, r0, [r1]
        ^

Change-Id: I65a91ed5a4461eca6646df13642a87a5c37d6c85