x86/apic/uv: Update the APIC UV OEM check

Optimize the first "SGI" OEM check to return faster if the
system is not an SGI or UV system.
Signed-off-by: Mike Travis <travis@sgi.com>
Acked-by: Hedi Berriche <hedi@sgi.com>
Acked-by: Dimitri Sivanich <sivanich@sgi.com>
Link: http://lkml.kernel.org/r/20150409182628.952357922@asylum.americas.sgi.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/kernel/apic/x2apic_uv_x.c

@@ -146,6 +146,9 @@ static int __init uv_acpi_madt_oem_check(char *oem_id, char *oem_table_id)
 {
 	int pnodeid, is_uv1, is_uv2, is_uv3;
 
+	if (strncmp(oem_id, "SGI", 3) != 0)
+		return 0;
+
 	is_uv1 = !strcmp(oem_id, "SGI");
 	is_uv2 = !strcmp(oem_id, "SGI2");
 	is_uv3 = !strncmp(oem_id, "SGI3", 4);	/* there are varieties of UV3 */