x86/boot/compressed/64: Define __force_order only when CONFIG_RANDOMIZE_BASE is unset

kaslr_64.c also defines the same variable, however when both files are
included into final link, linker complains about multiple definition of
`__force_order' which is coming from kaslr_64.o and pgtable_64.o, its
possible that kaslr_64.o is disabled via CONFIG_RANDOMIZE_BASE config
option, therefore define it conditionally only when
CONFIG_RANDOMIZE_BASE is not set

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: x86-ml <x86@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>