x86: acpi: Change fill_header()

Rename fill_header() to acpi_fill_header() for consistency.
Change its signature to remove the 'length' parameter and
make it a public API.

Also remove the unnecessary include files, and improve the
AmlCode[] comment a little bit.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Stefan Roese <sr@denx.de>
Tested-by: Stefan Roese <sr@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/x86/include/asm/acpi_table.h b/arch/x86/include/asm/acpi_table.h
index c6688ea..5a829de 100644
--- a/arch/x86/include/asm/acpi_table.h
+++ b/arch/x86/include/asm/acpi_table.h
@@ -304,6 +304,7 @@
 
 /* These can be used by the target port */
 
+void acpi_fill_header(struct acpi_table_header *header, char *signature);
 unsigned long acpi_create_madt_lapics(unsigned long current);
 int acpi_create_madt_ioapic(struct acpi_madt_ioapic *ioapic, u8 id, u32 addr,
 			 u32 gsi_base);