[PATCH] i2c: exynos5: Fix getting the optional clock

[Chanho Park]

> "hsi2c_pclk" clock is optional and may not be present for some SoCs
> supported by this driver. Nevertheless, in case the clock is provided but
> some error happens during its getting, that error should be handled
> properly. Use devm_clk_get_optional() API for that. Also report possible
> errors using dev_err_probe() to handle properly -EPROBE_DEFER error (if
> clock provider is not ready by the time I2C probe function is executed).
> 
> Fixes: c93ac09df2a8 ("i2c: exynos5: Add bus clock support")
> Signed-off-by: Sam Protsenko <semen.protsenko at linaro.org>

Reviewed-by: Chanho Park <chanho61.park at samsung.com>