xen: make multicall debug boot time selectable

Today Xen multicall debugging needs to be enabled via modifying a
define in a source file for getting debug data of multicall errors
encountered by users.

Switch multicall debugging to depend on a boot parameter "xen_mc_debug"
instead, enabling affected users to boot with the new parameter set in
order to get better diagnostics.

With debugging enabled print the following information in case at least
one of the batched calls failed:
- all calls of the batch with operation, result and caller
- all parameters of each call
- all parameters stored in the multicall data for each call

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Message-ID: <20240710092749.13595-1-jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>