Allow the at24 driver to get configuration information from both OF and
ACPI by using the more generic device_property functions.
This change was inspired by the at25.c driver.

I have a custom board with a ST M24C02 EEPROM attached to an I2C bus.
With the following ACPI construct, this patch instantiates a working
instance of the driver.

Device (EEP0) {
 Name (_HID, "PRP0001")
 Name (_DSD, Package () {
  ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
  Package () {
   Package () {"compatible", Package () {"st,24c02"}},
   Package () {"pagesize", 16},
  },
 })
 Name (_CRS, ResourceTemplate () {
  I2cSerialBus (
   0x0057, ControllerInitiated, 400000,
   AddressingMode7Bit, "\\_SB.PCI0.I2C3", 0x00,
   ResourceConsumer,,)
 })
}
Signed-off-by: Ben Gardner <gardner.ben@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>