spi: xilinx_spi: Perform software reset during slave setup

to make sure it is in the clear state.

Signed-off-by: Jason Wu <huanyu@xilinx.com>
diff --git a/drivers/spi/xilinx_spi.c b/drivers/spi/xilinx_spi.c
index 52a4134..db01cc2 100644
--- a/drivers/spi/xilinx_spi.c
+++ b/drivers/spi/xilinx_spi.c
@@ -99,6 +99,8 @@
 	debug("%s: bus:%i cs:%i base:%p mode:%x max_hz:%d\n", __func__,
 		bus, cs, xilspi->regs, xilspi->mode, xilspi->freq);
 
+	writel(SPISSR_RESET_VALUE, &xilspi->regs->srr);
+
 	return &xilspi->slave;
 }