hcrypto: Avoid 'double' param in arm64 kernel code

hcrypto: Avoid 'double' param in arm64 kernel code

Currently, the RAND_add function in hcrypto uses a floating point
argument (specifically, a 'double'), as well as any implementations of
RAND_add. On Linux arm64, we cannot use floating point code in the
kernel, since the kernel module is compiled with -mgeneral-regs-only,
which prevents the use of floating point registers. No code in the
tree actually makes use of this argument, but its mere presence is
enough to cause an error with at least some versions of gcc with
certain arguments.

To get around this, simply change all instances of 'double' in hcrypto
to be a void pointer instead. This allows the code to compile as long
as nobody actually uses that argument in the kernel. If the code is
changed such that we do actually use that argument, the argument will
be a void* and so will probably (hopefully) cause a compiler error,
and the code will need to be examined to make sure this workaround
doesn't break anything.

We already do this on Solaris, which has similar issues for different
compiler versions and compiler flags. Add arm64 Linux to the cases
where we do this, but restrict this to kernel code only, to try to
avoid doing this more often than necessary.

Change-Id: Ifd10786cd9ac6c9d5152b927e180b7362131f359
Reviewed-on: https://gerrit.openafs.org/11939
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>