wl18xx: add checks on wl18xx_top_reg_write() return value

Check return value from call to wl18xx_top_reg_write(),
so in case of error jump to goto label out and return.

Also, remove unnecessary value check before goto label out.

Addresses-Coverity-ID: 1226938
Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>