ENGR00252782 mxc v4l2 capture:Support csi number attribution

ENGR00252782 mxc v4l2 capture:Support csi number attribution

This patch adds device attribution for video device to
show csi number to userspace. The pattern is in "ipux_csix"
fashion, which tells which ipu and csi is relevant to a
specific video device. In this way, userspace may figure
out different cameras even if they have the same type,
especially, android may use this to know back/front
cameras.

Signed-off-by: Liu Ying <Ying.Liu@freescale.com>