KVM: PPC: Book3S HV: XIVE: Fix spelling mistake "acessing" -> "accessing"

There is a spelling mistake in a pr_err message, fix it.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>