manifest: Track s4-common repo for evita

Reorganization to add in m7 to current existing msm8960 HTC trees has created
a new s4-common repository.

Fork repo from https://github.com/rohanmathur/device_htc_s4-common and create gerrit project

Change-Id: I08b0458da3c99ec7fd6c9e43bee9593804f5e2b4
Signed-off-by: Rohan Mathur <rohanmathur34@gmail.com>