efi/efivar_ssdt_load: Don't return success on allocation failure

We should return -ENOMEM here, instead of success.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Fixes: 475fb4e8

 ("efi / ACPI: load SSTDs from EFI variables")
Link: http://lkml.kernel.org/r/20161018143318.15673-9-matt@codeblueprint.co.uk
Signed-off-by: Ingo Molnar <mingo@kernel.org>