brcmfmac: Delete unnecessary variable initialisation

In brcmf_sdio_download_firmware(), bcmerror is set by the call to
brcmf_sdio_download_code_file(), before it's checked in the following
line.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Acked-by: Arend van Spriel <arend@broadcom.com>
[Rewrote commit message]
Signed-off-by: Julian Calaby <julian.calaby@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>