i2c: Bugfix in i2c_get_chip_by_phandle()

The "i2cbcdev" sneaked in when implementing this function for the
bootcounter use case. Obviously the intention was to use prop_name
instead.

Fixes: b4835527 (i2c: Implement i2c_get_chip_by_phandle())

Signed-off-by: Philip Oberfichtner <pro@denx.de>
Acked-by: Heiko Schocher <hs@denx.de>