fix radeon setparam on 32/64 systems, harder.

    Commit 9b01bd5b284bbf519b726b39f1352023cb5e9e69 introduced a
    compat_ioctl handler for RADEON_SETPARAM, the sole purpose of which was
    to handle the fact that on i386, alignof(uint64_t)==4.

    Unfortunately, this handler was installed for _all_ 64-bit
    architectures, instead of only x86_64 and ia64.  And thus it breaks
    32-bit compatibility on every other arch, where 64-bit integers are
    aligned to 8 bytes in 32-bit mode just the same as in 64-bit mode.

    Arnd has a cunning plan to use 'compat_u64' with appropriate alignment
    attributes according to the 32-bit ABI, but for now let's just make the
    compat_radeon_cp_setparam routine entirely disappear on 64-bit machines
    whose 32-bit compat support isn't for i386.  It would be a no-op with
    compat_u64 anyway.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>