xen: Fix implicit type conversion

xen: Fix implicit type conversion

The variable 'i' is defined as UINT. However, in the for_each_possible_cpu
its value is assigned to -1. That doesn't make sense and in the
cpumask_next() it is implicitly type converted to INT. It is universally
accepted that the implicit type conversion is terrible. Also, having the
good programming custom will set an example for others. Thus, it might be
better to change the definition of 'i' from UINT to INT.

[boris: fixed commit message formatting]

Fixes: 3fac10145b76 ("xen: Re-upload processor PM data to hypervisor after S3 resume (v2)")
Signed-off-by: Jiasheng Jiang <jiasheng@iscas.ac.cn>
Link: https://lore.kernel.org/r/1635233531-2437704-1-git-send-email-jiasheng@iscas.ac.cn
Reviewed-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jiamei Xie <jiamei.xie@arm.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>