msm: camera: isp: Support of Y8 format for IFE FD port

Add support of Y8 format for IFE FD port, so that
we may set IFE FD port to output Y8 instead of YUV.
This is because FD does not need UV.

Change-Id: I7f748845a059e3a55a0da6703fc0825af6c701b5
Signed-off-by: Yizheng Zhou <yizhengz@codeaurora.org>