spi: mt65xx: Support per spi-mem operation frequency switches

Every ->exec_op() call correctly configures the spi bus speed to the
maximum allowed frequency for the memory using the constant spi default
parameter. Since we can now have per-operation constraints, let's use
the value that comes from the spi-mem operation structure instead. In
case there is no specific limitation for this operation, the default spi
device value will be given anyway.

The per-operation frequency capability is thus advertised to the spi-mem
core.

Cc: Matthias Brugger <[e-mail]>
Signed-off-by: Miquel Raynal <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Mark Brown <[e-mail]>

drivers/spi/spi-mt65xx.c

···
 
 	mtk_spi_reset(mdata);
 	mtk_spi_hw_init(mem->spi->controller, mem->spi);
-	mtk_spi_prepare_transfer(mem->spi->controller, mem->spi->max_speed_hz);
+	mtk_spi_prepare_transfer(mem->spi->controller, op->max_freq);
 
 	reg_val = readl(mdata->base + SPI_CFG3_IPM_REG);
 	/* opcode byte len */
···
 	.exec_op = mtk_spi_mem_exec_op,
 };
 
+static const struct spi_controller_mem_caps mtk_spi_mem_caps = {
+	.per_op_freq = true,
+};
+
 static int mtk_spi_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
···
 	if (mdata->dev_comp->ipm_design) {
 		mdata->dev = dev;
 		host->mem_ops = &mtk_spi_mem_ops;
+		host->mem_caps = &mtk_spi_mem_caps;
 		init_completion(&mdata->spimem_done);
 	}