[PowerPC] fatal error: error in backend: Unknown mismatch in getCopyFromParts!

FreeBSD 15.0-RELEASE
powerpc, powerpc64, powerpc64le
LLVM 22.0.d20260113

Reproducer:

```c
int main(void)
{
unsigned short bits = 0xFF;
double f;
__asm__ __volatile__("xscvhpdp %x0,%x1" : "=wa"(f) : "wa"(bits));
__asm__ __volatile__ ("xscvdphp %x0,%x1" : "=wa" (bits) : "wa" (f));
return bits;
}
```

Compile with:
`/usr/bin/cc -cc1 -triple powerpc-unknown-freebsd15.0 -emit-obj -target-cpu pwr7 extra_vsx3_half_double-3c71c3.c`

Output:
`fatal error: error in backend: Unknown mismatch in getCopyFromParts!`