x86: acpi: Make enter_acpi_mode() public

enter_acpi_mode() is useful on other boot path like S3 resume, so
make it public.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Stefan Roese <sr@denx.de>
diff --git a/arch/x86/lib/acpi_table.c b/arch/x86/lib/acpi_table.c
index 8be8120..87a71ca 100644
--- a/arch/x86/lib/acpi_table.c
+++ b/arch/x86/lib/acpi_table.c
@@ -304,7 +304,7 @@
 	header->checksum = table_compute_checksum((void *)mcfg, header->length);
 }
 
-static void enter_acpi_mode(int pm1_cnt)
+void enter_acpi_mode(int pm1_cnt)
 {
 	u16 val = inw(pm1_cnt);