x86: acpi: Export acpi_fill_mcfg() with __weak attribute

Some platforms might require different approach when filling memory
mappings configuration table.

Allow them to override the common method.

At the same time export acpi_create_mcfg_mmconfig().

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/arch/x86/include/asm/acpi_table.h b/arch/x86/include/asm/acpi_table.h
index e177c44..8003850 100644
--- a/arch/x86/include/asm/acpi_table.h
+++ b/arch/x86/include/asm/acpi_table.h
@@ -314,6 +314,9 @@
 int acpi_create_madt_lapic_nmi(struct acpi_madt_lapic_nmi *lapic_nmi,
 			       u8 cpu, u16 flags, u8 lint);
 u32 acpi_fill_madt(u32 current);
+int acpi_create_mcfg_mmconfig(struct acpi_mcfg_mmconfig *mmconfig, u32 base,
+			      u16 seg_nr, u8 start, u8 end);
+u32 acpi_fill_mcfg(u32 current);
 void acpi_create_gnvs(struct acpi_global_nvs *gnvs);
 /**
  * enter_acpi_mode() - enter into ACPI mode