wifi: ath11k: mhi: fix potential memory leak in ath11k_mhi_register()

In the Linux kernel, the following vulnerability has been resolved: wifi: ath11k: mhi: fix potential memory leak in ath11k_mhi_register() mhi_alloc_controller() allocates a memory space for mhi_ctrl. When gets some error, mhi_ctrl should be freed with mhi_free_controller(). But when ath11k_mhi_read_addr_from_dt() fails, the function returns without calling mhi_free_controller(), which will lead to a memory leak. We can fix it by calling mhi_free_controller() when ath11k_mhi_read_addr_from_dt() fails.