simd_powerpc.h: enable FPU on FreeBSD

[pkubaj]

FreeBSD nowadays supports FPU in the kernel on powerpc*, so enable it.

Including machine/pcpu.h needs to be done before including sys/types.h, hence this order.

Motivation and Context

It enables ZFS to use assembly routines with SIMD.

Description

How Has This Been Tested?

Booting with ZFS on root on POWER9 workstation.

FreeBSD 14.2-RELEASE on POWER9, ZFS on /.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Performance enhancement (non-breaking change which improves efficiency)
• Code cleanup (non-breaking change which makes code smaller or more readable)
• Breaking change (fix or feature that would cause existing functionality to change)
• Library ABI change (libzfs, libzfs_core, libnvpair, libuutil and libzfsbootenv)
• Documentation (a change to man pages or other documentation)

Checklist:

• My code follows the OpenZFS code style requirements.
• I have updated the documentation accordingly.
• I have read the contributing document.
• I have added tests to cover my changes.
• I have run the ZFS Test Suite with this change applied.
• All commit messages are properly formatted and contain Signed-off-by.

[amotin]

I see you've committed it to FreeBSD before waiting for review here. I'll pass it this time, but you haven't even answered to one of my comments, so I assume you know what you are doing and there won't be a followup commit.

[pkubaj]

Sorry, I didn't notice your comment before committing to FreeBSD.
Inclusion of machine/pcpu.h was necessary in the earlier version of the patch but it looks like after I removed some later includes, it's not necessary anymore.