Revert "mfd: syscon: Remove repetition of the regmap_get_val_endian()"

This reverts commit 72a9585.

It broke reboots on big-endian MIPS and MIPS64 malta QEMU instances,
which use the syscon driver.  Little-endian is not effected, which means
likely it's important to handle regmap_get_val_endian() in this function
after all.

Fixes: 72a9585 ("mfd: syscon: Remove repetition of the regmap_get_val_endian()")
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Lee Jones <lee@kernel.org>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/mfd/syscon.c

@@ -66,6 +66,14 @@ static struct syscon *of_syscon_register(struct device_node *np, bool check_clk)
 		goto err_map;
 	}
 
+	/* Parse the device's DT node for an endianness specification */
+	if (of_property_read_bool(np, "big-endian"))
+		syscon_config.val_format_endian = REGMAP_ENDIAN_BIG;
+	else if (of_property_read_bool(np, "little-endian"))
+		syscon_config.val_format_endian = REGMAP_ENDIAN_LITTLE;
+	else if (of_property_read_bool(np, "native-endian"))
+		syscon_config.val_format_endian = REGMAP_ENDIAN_NATIVE;
+
 	/*
 	 * search for reg-io-width property in DT. If it is not provided,
 	 * default to 4 bytes. regmap_init_mmio will return an error if values