msm: vidc: Set default value for work route

Work route is considered during  instance load calculations.
If work route is not set, load will be calculated incorrectly.
For AR50 based targets work route should be considered as 1.
Adding default initialization to 1.

Change-Id: Ia17c0f21f3ffae1837265826230b8f98b68880d5
Signed-off-by: Aniket Masule <amasule@codeaurora.org>
Signed-off-by: Priyanka Gujjula <pgujjula@codeaurora.org>