drm/dsi-staging: enable DSI_PARSER sub-module

Enable the compilation of DSI_PARSER sub-module which is
a text parser and is used for parsing the panel configurations.

CRs-Fixed: 2223812
Change-Id: I2c3403ebbcfd6b6aa9db449e01567645dc756dc5
Signed-off-by: Ajay Singh Parmar <aparmar@codeaurora.org>