We have a sh_spi_clear_bit() function, there's no reason not to use it.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Acked-by: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
Reviewed-by: Jagannadha Sutradharudu Teki <jaganna@xilinx.com>