In some case, the GDDV returns a package with a buffer which has
zero length. It causes that kmemdup() returns ZERO_SIZE_PTR (0x10).

Then the data_vault_read() got NULL point dereference problem when
accessing the 0x10 value in data_vault.

[   71.024560] BUG: kernel NULL pointer dereference, address:
0000000000000010

This patch uses ZERO_OR_NULL_PTR() for checking ZERO_SIZE_PTR or
NULL value in data_vault.
Signed-off-by: "Lee, Chun-Yi" <jlee@suse.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>