mailbox: qcom-ipcc: fix incorrect num_chans counting

Breaking out early when a match is found leads to an incorrect num_chans
value when more than one ipcc mailbox channel is used by the same device.

Fixes: e9d50e4b ("mailbox: qcom-ipcc: Dynamic alloc for channel arrangement")
Signed-off-by: Jonathan Marek <jonathan@marek.ca>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>