nl80211: nl80211hdr_put() doesn't return an ERR_PTR

There are a few places which check nl80211hdr_put() for an ERR_PTR

but actually it returns NULL on error and never error values.  In

nl80211_testmode_dump() the return wasn't checked at all so I have

added one.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

[some whitespace changes]

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

Git-commit: cb35fba

Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git

Change-Id: I5da1aafea35110a1ce606d402b1b96859d34b869

[akholaif@codeaurora.org: resolved conflicts manually]

Signed-off-by: Ahmad Kholaif <akholaif@codeaurora.org>