spi: rspi: Do not set SPCR_SPE in qspi_set_config_register()

The R-Car Gen2 Hardware User Manual Rev. 2.00 states:

    If the master/slave mode select bit (MSTR) is modified while the SPI
    function enable bit (SPE) is set to 1 (that is, this module is
    enabled), the subsequent operation cannot be guaranteed.

Hence do not set SPCR_SPE when setting SPCR_MSTR, just like the
.set_config_register() implementations for other RSPI variants do.

Note that when booted from QSPI, the boot loader will have set SPCR_MSTR
already, hence usually the bit is never modified by the Linux driver.

Reported-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-rspi.c

@@ -377,8 +377,8 @@ static int qspi_set_config_register(struct rspi_data *rspi, int access_size)
 	/* Sets SPCMD */
 	rspi_write16(rspi, rspi->spcmd, RSPI_SPCMD0);
 
-	/* Enables SPI function in master mode */
-	rspi_write8(rspi, SPCR_SPE | SPCR_MSTR, RSPI_SPCR);
+	/* Sets RSPI mode */
+	rspi_write8(rspi, SPCR_MSTR, RSPI_SPCR);
 
 	return 0;
 }