Revert "msm: mdss: Find a stable sysfs node for the gamma interface"

This reverts commit da0bf0d0f9162502302cf902609e3e3f3eebd203.

Conflicts:
	drivers/video/msm/mdss/mdss_dsi_panel.c

Change-Id: I2127af612dfd72a77c1a95ddbcdf5e5118f8a7d1