x86/mpparse: Don't print "limit reached" for every subsequent processor

x86/mpparse: Don't print "limit reached" for every subsequent processor

When you boot Xen with the default 256 NR_CPUS, on a box with rather more
processors, the resulting spew is unnecesserily verbose.  Instead, print the
message once, e.g:

 (XEN) ACPI: X2APIC (apic_id[0x115] uid[0x115] enabled)
 (XEN) WARNING: NR_CPUS limit of 256 reached - ignoring further processors
 (XEN) ACPI: X2APIC (apic_id[0x119] uid[0x119] enabled)
 (XEN) ACPI: X2APIC (apic_id[0x11d] uid[0x11d] enabled)
 (XEN) ACPI: X2APIC (apic_id[0x121] uid[0x121] enabled)

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>