bloblist: fix pointer comparison in bloblist_apply_blobs()

bloblist: fix pointer comparison in bloblist_apply_blobs()

The rec_from_blob() function returns a pointer, but the code was
comparing it using "rec <= 0" which is incorrect for pointer types.
Pointers should be compared using "== NULL" or "!= NULL".

Addresses-Coverity-ID: CID 645841: Incorrect expression (BAD_COMPARE)
Signed-off-by: Michal Simek <michal.simek@amd.com>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Reviewed-by: Raymond Mao <raymondmaoca@gmail.com>