msm: vidc: Register new nodes to support q6 hfi

Add support for different node values for simultaneous
venus and q6 usecase. This is needed to support HEVC
decode on msm8974, where venus and q6 both will be
present. Also create "link_name" device attribute
to provide a meaningful name to the video device
instead of video32, video33 etc. Userspace reads
this "link_name" sysfs node and creates appropiate
dev node symbolic link.

Change-Id: Iab14cad2c43b78eb7553ac78521611727597a42f
Signed-off-by: Sachin Shah <sachins@codeaurora.org>