[ARM] Allow setting the generic features for native cpus
Copying the already existing code for x86 to ARM to set the correct CPU
features when using -mcpu=native. We can already detect the CPU name
but we were not setting the correct feature bits.
Moving fpu/hwdiv down to make sure they override whatever we set the
default to be.
No tests because this is native detection, and not all ARM-enabled builds
will hapen at a specific CPU, or even ARM. I have tested locally and it
works as expected.
Fixes PR12794.
llvm-svn: 243656