arch:x86:xen: Remove unnecessary assignment in xen_apic_read()

In the function xen_apic_read(), the initialized value of 'ret' is unused
because it will be assigned by the function HYPERVISOR_platform_op(),
thus remove it.

Signed-off-by: jianchunfu <jianchunfu@cmss.chinamobile.com>
Link: https://lore.kernel.org/r/20220314070514.2602-1-jianchunfu@cmss.chinamobile.com


Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>