i2c: jz4780: Fix return value if probe fails

Current code returns 0 if fails to read clock-frequency DT property,
fix it. Also add checking return value of clk_prepare_enable and
propagate return value of devm_request_irq.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>