x86: ich-spi: Remove useless assignment in ich_spi_xfer()

In ich_spi_xfer() when the driver presets control fields, control
variable gets assigned twice. Apparently only the last assignment
takes effect. Remove the other one.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Stefan Roese <sr@denx.de>