rsi: Fix possible leak when loading firmware

Commit 5d5cd85f ("rsi: Fix failure to load firmware after memory
leak fix and fix the leak") also added a check on the allocation of
DMA-accessible memory that may directly return. In that case the
already allocated firmware data is leaked. Make sure the data is
always freed correctly. Detected by Coverity CID 1316519.

Fixes: 5d5cd85f ("rsi: Fix failure to load firmware after memory leak fix and fix the leak")
Signed-off-by: Christian Engelmayer <cengelma@gmx.at>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>