bus: mhi: core: Fix null pointer access when parsing MHI configuration

Functions parse_ev_cfg() and parse_ch_cfg() access mhi_cntrl->mhi_dev
before it is set in function mhi_register_controller(),
use cntrl_dev instead of mhi_dev.

Fixes: 0cbf2608 ("bus: mhi: core: Add support for registering MHI controllers")
Signed-off-by: Carl Yin <carl.yin@quectel.com>
Reviewed-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
Reviewed-by: Hemant Kumar <hemantk@codeaurora.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>