mwifiex: avoid freeing improper pointer in mwifiex_set_wowlan_mef_entry

mwifiex_set_wowlan_mef_entry attempts to free a passed-in pointer in
case of an error.  The only caller (mwifiex_set_mef_filter) passes that
pointer as an offset into allocated memory, so any attempt to free that
will not be the actual allocated pointer.

Address this by changing mwifiex_set_wowlan_mef_entry to not do any
free, and to cause mwifiex_set_mef_filter to do the appropriate free if
the call to mwifiex_set_wowlan_mef_entry fails.

Coverity CID #1295879

Signed-off-by: John W. Linville <linville@tuxdriver.com>
Acked-by: Amitkumar Karwar <akarwar@marvell.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>