cmov: fix aarch64 ASM bug; add regression test

[tarcieri]

The implementation was using the wrong register type when invoking csel for u64 (:w which is 32-bit, should use :x for 64-bit)

This captures the bug in a regression test and fixes it.

[tarcieri]

The PPC failure is probably the same issue as #1298.

GitHub Actions killed the aarch64 runs but they're also failing:

https://github.com/RustCrypto/utils/actions/runs/20548849075/job/59023609534?pr=1299

Run cross test --target aarch64-unknown-linux-gnu
[...]
     Running tests/regression.rs (/target/aarch64-unknown-linux-gnu/debug/deps/regression-d4120ddf24ad0571)

running 1 test
test u64_cmoveq ... FAILED

failures:

---- u64_cmoveq stdout ----

thread 'u64_cmoveq' panicked at cmov/tests/regression.rs:12:5:
assertion `left == right` failed
  left: 1
 right: 0
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

I sprinkled some dbg! into the u64 impls in aarch64.rs like so:

#[inline]
fn cmoveq(&self, rhs: &Self, input: Condition, output: &mut Condition) {
    dbg!(self, rhs, input, &output);
    csel_eq!("csel {3:w}, {4:w}, {5:w}, EQ", self, rhs, input, output);
}

It's definitely getting called, here's the output:

---- u64_cmoveq stdout ----
[cmov/src/aarch64.rs:110:9] self = 9367487224930631680
[cmov/src/aarch64.rs:110:9] rhs = 0
[cmov/src/aarch64.rs:110:9] input = 1
[cmov/src/aarch64.rs:110:9] &output = 0

thread 'u64_cmoveq' panicked at cmov/tests/regression.rs:12:5:
assertion `left == right` failed
  left: 1
 right: 0
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

cc @brxken128 @codahale who worked on the aarch64 impl

[tarcieri]

It seems the registers should be :x instead of :w but that doesn't seem to actually fix the problem

Edit: aah, looks like the other macros hardcode :w too and that might need to be changed to :x?

Edit again: confirm changing all of the asm registers from :w to :x fixes the problem