efi: ssdt: Don't free memory if ACPI table was loaded successfully

In the Linux kernel, the following vulnerability has been resolved:

efi: ssdt: Don't free memory if ACPI table was loaded successfully

Amadeusz reports KASAN use-after-free errors introduced by commit

3881ee0b1edc ("efi: avoid efivars layer when loading SSDTs from

variables"). The problem appears to be that the memory that holds the

new ACPI table is now freed unconditionally, instead of only when the

ACPI core reported a failure to load the table.

So let's fix this, by omitting the kfree() on success.