bus: mhi: core: Use appropriate label in firmware load handler API

Correct the "error_read" label to say "error_ready_state" as that
is the appropriate usage of the label.

Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>