input: touchpanel: Add Mstar msg21xx touchpanel driver

This is the reference driver source code for the msg21xx series.

Signed-off-by: Bruce Ding <bruce.ding@mstarsemi.com>
Signed-off-by: mstar-touch <bruce.ding@mstarsemi.com>
Git-commit: c4cdbf1ae326b8745f5e50f044d23aa8e3d3e131
Git-repo: https://github.com/mstar-touch/msg21xx



Change-Id: Ia9cbfac5dc6e1b74f47bf13dbafaacc2624ee4fd
[maol@codeaurora.org: keep the mstar original code without any
change in this commit]
Signed-off-by: Mao Li <maol@codeaurora.org>
Signed-off-by: Sudhakar Manapati <smanap@codeaurora.org>