checks: Remove warning for I2C_OWN_SLAVE_ADDRESS

dtc does a sanity check on reg properties that they are within the 10
bit address range for i2c slave addresses. In the case of multi-master
buses or devices that act as a slave, the binding may describe an
address that the bus will listen on as a device. Do not warn when this
flag is set.

See Documentation/devicetree/bindings/i2c/i2c.txt.

This fixes the following build warnings reported by Stephen and by Arnd:

arch/arm/boot/dts/aspeed-bmc-facebook-yosemitev2.dts:126.11-130.4:
  Warning (i2c_bus_reg): /ahb/apb/bus@1e78a000/i2c-bus@80/ipmb1@10:
    I2C bus unit address format error, expected "40000010"
arch/arm/boot/dts/aspeed-bmc-facebook-yosemitev2.dts:128.3-30:
  Warning (i2c_bus_reg): /ahb/apb/bus@1e78a000/i2c-bus@80/ipmb1@10:reg:
    I2C address must be less than 10-bits, got "0x40000010"

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Joel Stanley <joel@jms.id.au>
Message-Id: <20200622031005.1890039-2-joel@jms.id.au>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

checks.c

@@ -1022,6 +1022,8 @@ static void check_i2c_bus_bridge(struct check *c, struct dt_info *dti, struct no
 }
 WARNING(i2c_bus_bridge, check_i2c_bus_bridge, NULL, &addr_size_cells);
 
+#define I2C_OWN_SLAVE_ADDRESS	(1U << 30)
+
 static void check_i2c_bus_reg(struct check *c, struct dt_info *dti, struct node *node)
 {
 	struct property *prop;
@@ -1044,6 +1046,8 @@ static void check_i2c_bus_reg(struct check *c, struct dt_info *dti, struct node
 	}
 
 	reg = fdt32_to_cpu(*cells);
+	/* Ignore I2C_OWN_SLAVE_ADDRESS */
+	reg &= ~I2C_OWN_SLAVE_ADDRESS;
 	snprintf(unit_addr, sizeof(unit_addr), "%x", reg);
 	if (!streq(unitname, unit_addr))
 		FAIL(c, dti, node, "I2C bus unit address format error, expected \"%s\"",
@@ -1051,6 +1055,8 @@ static void check_i2c_bus_reg(struct check *c, struct dt_info *dti, struct node
 
 	for (len = prop->val.len; len > 0; len -= 4) {
 		reg = fdt32_to_cpu(*(cells++));
+		/* Ignore I2C_OWN_SLAVE_ADDRESS */
+		reg &= ~I2C_OWN_SLAVE_ADDRESS;
 		if (reg > 0x3ff)
 			FAIL_PROP(c, dti, node, prop, "I2C address must be less than 10-bits, got \"0x%x\"",
 				  reg);