x86/xen/time: Reduce Xen timer tick

Current timer tick is causing some deadline to fail.
The current high value constant was probably due to an old
bug in the Xen timer implementation causing errors if the
deadline was in the future.

This was fixed in Xen commit:
19c6cbd90965 xen/vcpu: ignore VCPU_SSHOTTMR_future

Usage of VCPU_SSHOTTMR_future in Linux kernel was removed by:
c06b6d70 xen/x86: don't lose event interrupts

Signed-off-by: Frediano Ziglio <frediano.ziglio@cloud.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20240619104015.30477-1-frediano.ziglio@cloud.com


Signed-off-by: Juergen Gross <jgross@suse.com>