x86: limit number of hypercall parameters to 5

x86: limit number of hypercall parameters to 5

Today there is no hypercall with more than 5 parameters, while the ABI
allows up to 6 parameters. Especially for the X86 32-bit case using
6 parameters would require to run without frame pointer, which isn't
very fortunate. Note that for Arm the limit is 5 parameters already.

So limit the maximum number of parameters to 5 for x86, too.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>