msm: camera: isp: Use max stream src based on VFE output

Stream info holds information about various axi outputs
but maximum streams VFE can output is limited by write masters.
Use correct macros to differentiate between two.

Change-Id: I264e8ef6b77e0f5a1fff1c7114d53d017375aa78
Signed-off-by: Sagar Gore <sgore@codeaurora.org>
Signed-off-by: Harsh Shah <harshs@codeaurora.org>