spi: add support for ARM PL022 SPI controller

This adds support for the ARM PL022 SPI controller for the standard
variant (0x00041022) which has a 16bit wide and 8 locations deep TX/RX
FIFO.

A few parts were borrowed from the Linux kernel driver.

Cc: Armando Visconti <armando.visconti@st.com>
Cc: Vipin Kumar <vipin.kumar@st.com>
Signed-off-by: Quentin Schulz <quentin.schulz@bootlin.com>

include/dm/platform_data/pl022_spi.h

@@ -0,0 +1,28 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * (C) Copyright 2018
+ * Quentin Schulz, Bootlin, quentin.schulz@bootlin.com
+ *
+ * Structure for use with U_BOOT_DEVICE for pl022 SPI devices or to use
+ * in ofdata_to_platdata.
+ */
+
+#ifndef __PL022_SPI_H__
+#define __PL022_SPI_H__
+
+#if !CONFIG_IS_ENABLED(OF_PLATDATA)
+#include <clk.h>
+#endif
+#include <fdtdec.h>
+
+struct pl022_spi_pdata {
+	fdt_addr_t addr;
+	fdt_size_t size;
+#if !CONFIG_IS_ENABLED(OF_PLATDATA)
+	struct clk clk;
+#else
+	unsigned int freq;
+#endif
+};
+
+#endif