i2c: powermac: Simplify reading the "reg" and "i2c-address" property

Use of_property_read_u32 to read the "reg" and "i2c-address" property
instead of using of_get_property to check the return values.

Signed-off-by: Aishwarya R <aishwaryarj100@gmail.com>
Tested-by: Erhard Furtner <erhard_f@mailbox.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>