iwlwifi: actually check allocated conf_tlv pointer

Commit 71bc0334 ("iwlwifi: check allocated pointer when allocating
conf_tlvs") attempted to fix a typoe introduced by commit 17b809c9
("iwlwifi: dbg: move debug data to a struct") but does not implement the
check correctly.

Fixes: 71bc0334 ("iwlwifi: check allocated pointer when allocating conf_tlvs")
Tweeted-by: @grsecurity
Signed-off-by: Chris Rorvick <chris@rorvick.com>
Signed-off-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200417074558.12316-1-sedat.dilek@gmail.com