spi: mxic: 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.

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

drivers/spi/spi-mxic.c

···
 	int i, ret;
 	u8 addr[8], cmd[2];
 
-	ret = mxic_spi_set_freq(mxic, mem->spi->max_speed_hz);
+	ret = mxic_spi_set_freq(mxic, op->max_freq);
 	if (ret)
 		return ret;
 
···
 	.dtr = true,
 	.ecc = true,
 	.swap16 = true,
+	.per_op_freq = true,
 };
 
 static void mxic_spi_set_cs(struct spi_device *spi, bool lvl)