wil6210: print error in FW and board files load failures

Add an error print-out in case FW and board files load fails,
as such an error is not printed on all failures and user may
not understand why the interface up operations didn't succeed.

Signed-off-by: Maya Erez <merez@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>