aarch64: Fix testcase vec-init-22-speed.c [PR116589]

For this testcase, the trunk produces:
```
f_s16:
        fmov    s31, w0
        fmov    s0, w1
```

While the testcase was expecting what was produced in GCC 14:
```
f_s16:
        sxth    w0, w0
        sxth    w1, w1
        fmov    d31, x0
        fmov    d0, x1
```

After r15-1575-gea8061f46a30 the code was:
```
        dup     v31.4h, w0
        dup     v0.4h, w1
```
But when ext-dce was added with r15-1901-g98914f9eba5f19, we get the better code generation now and only fmov's.

Pushed as obvious after running the testcase.

	PR target/116589

gcc/testsuite/ChangeLog:

	* gcc.target/aarch64/vec-init-22-speed.c: Update scan for better code gen.

Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>