[efi] Fix typo in efi_acpi_table_protocol_guid

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/interface/efi/efi_guid.c

 	= EFI_ABSOLUTE_POINTER_PROTOCOL_GUID;
 
 /** ACPI table protocol GUID */
-EFI_GUID efi_acpi_table_protocl_guid
+EFI_GUID efi_acpi_table_protocol_guid
 	= EFI_ACPI_TABLE_PROTOCOL_GUID;
 
 /** Apple NetBoot protocol GUID */