msm: mhi_dev: Disabling Ch Db Intr during MHI INIT phase

In order to tackle the spurious interrupts coming from the host
on an invalid channel, the channel doorbell interrupts are
disabled during initialization phase. These are enabled after
receiving the start command for a particular channel.

Change-Id: I12bb315bcd249383ed442ad969e84c9eef25a324
Signed-off-by: Abhinab Abhinab <aabhinab@codeaurora.org>
Signed-off-by: Gauri Joshi <gaurjosh@codeaurora.org>