staging: wilc1000: fix missing read_write setting when reading data

Currently the cmd.read_write setting is not initialized so it contains
garbage from the stack.  Fix this by setting it to 0 to indicate a
read is required.

Detected by CoverityScan, CID#1357925 ("Uninitialized scalar variable")

Fixes: c5c77ba1 ("staging: wilc1000: Add SDIO/SPI 802.11 driver")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Cc: stable <stable@vger.kernel.org>
Acked-by: Ajay Singh <ajay.kathat@microchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>