mhi: dev: uci: remove boot logger channel from userspace

External modem boot logs will be routed to ipc logging buffer
instead of userspace.

CRs-Fixed: 2299820
Change-Id: Ib8fc6896f9ec3e0560409422b031ae9ac60e5c71
Signed-off-by: Sujeev Dias <sdias@codeaurora.org>