xen/events: Cleanup find_virq() return codes

xen/events: Cleanup find_virq() return codes

rc is overwritten by the evtchn_status hypercall in each iteration, so
the return value will be whatever the last iteration is.  This could
incorrectly return success even if the event channel was not found.
Change to an explicit -ENOENT for an un-found virq and return 0 on a
successful match.

Fixes: 62cc5fc7b2e0 ("xen/pv-on-hvm kexec: rebind virqs to existing eventchannel ports")
Cc: stable@vger.kernel.org
Signed-off-by: Jason Andryuk <jason.andryuk@amd.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Message-ID: <20250828003604.8949-2-jason.andryuk@amd.com>