efi: Fix memory leak in efivar_ssdt_load

efi: Fix memory leak in efivar_ssdt_load

When we load SSDT from efi variable (specified with efivar_ssdt=<var>
boot command line argument) a name for the variable is allocated
dynamically because we traverse all EFI variables. Unlike ACPI table
data, which is later used by ACPI engine, the name is no longer needed
once traverse is complete -- don't forget to free this memory.

Same time we silently ignore any errors happened here let's print a
message if something went wrong (but do not exit since this is not a
critical error and the system should continue to boot).

Also while here -- add a note why we keep SSDT table on success.

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>