rtc: pcf2127: fix SPI command byte for PCF2131

PCF2131 was not responding to read/write operations using SPI. PCF2131
has a different command byte definition, compared to PCF2127/29. Added
the new command byte definition when PCF2131 is detected.

Fixes: afc505b ("rtc: pcf2127: add support for PCF2131 RTC")
Cc: stable@vger.kernel.org
Signed-off-by: Elena Popa <elena.popa@nxp.com>
Acked-by: Hugo Villeneuve <hvilleneuve@dimonoff.com>
Link: https://lore.kernel.org/r/20250530104001.957977-1-elena.popa@nxp.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

Author: elenap08

drivers/rtc/rtc-pcf2127.c

@@ -1538,6 +1538,11 @@ static int pcf2127_spi_probe(struct spi_device *spi)
 		variant = &pcf21xx_cfg[type];
 	}
 
+	if (variant->type == PCF2131) {
+		config.read_flag_mask = 0x0;
+		config.write_flag_mask = 0x0;
+	}
+
 	config.max_register = variant->max_register,
 
 	regmap = devm_regmap_init_spi(spi, &config);