x86: clean up apic->acpi_madt_oem_check methods

Impact: refactor code

x86 subarchitectures each defined a "acpi_madt_oem_check()" method,
which could be an inline function, or an extern, or a static function,
and which was also the name of a genapic field.

Untangle this namespace spaghetti by setting ->acpi_madt_oem_check()
to NULL on those subarchitectures that have no detection quirks,
and rename the other ones (summit, es7000) that do.

Also change default_acpi_madt_oem_check() to handle NULL entries,
and clean its control flow up as well.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/include/asm/mach-default/mach_mpparse.h b/arch/x86/include/asm/mach-default/mach_mpparse.h
index c70a263..8fa0177 100644
--- a/arch/x86/include/asm/mach-default/mach_mpparse.h
+++ b/arch/x86/include/asm/mach-default/mach_mpparse.h
@@ -8,7 +8,7 @@
 }
 
 /* Hook from generic ACPI tables.c */
-static inline int acpi_madt_oem_check(char *oem_id, char *oem_table_id)
+static inline int default_acpi_madt_oem_check(char *oem_id, char *oem_table_id)
 {
 	return 0;
 }