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/lib/acpi_table.c b/arch/x86/lib/acpi_table.c
index 14d10c3..da6014f 100644
--- a/arch/x86/lib/acpi_table.c
+++ b/arch/x86/lib/acpi_table.c
@@ -293,8 +293,8 @@
 	header->checksum = table_compute_checksum((void *)madt, header->length);
 }
 
-static int acpi_create_mcfg_mmconfig(struct acpi_mcfg_mmconfig *mmconfig,
-				     u32 base, u16 seg_nr, u8 start, u8 end)
+int acpi_create_mcfg_mmconfig(struct acpi_mcfg_mmconfig *mmconfig, u32 base,
+			      u16 seg_nr, u8 start, u8 end)
 {
 	memset(mmconfig, 0, sizeof(*mmconfig));
 	mmconfig->base_address_l = base;
@@ -306,7 +306,7 @@
 	return sizeof(struct acpi_mcfg_mmconfig);
 }
 
-static u32 acpi_fill_mcfg(u32 current)
+__weak u32 acpi_fill_mcfg(u32 current)
 {
 	current += acpi_create_mcfg_mmconfig
 		((struct acpi_mcfg_mmconfig *)current,