xen/livepatch: Use zeroed memory allocations for arrays

xen/livepatch: Use zeroed memory allocations for arrays

Each of these arrays is sparse.  Use zeroed allocations to cause uninitialised
array elements to contain deterministic values, most importantly for the
embedded pointers.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Tested-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> [x86 and arm32]
Reviewed-by: Ross Lagerwall <ross.lagerwall@citrix.com>