sdm: Fix handling disable lut generation

- When sdm.disable_hdr_lut_gen is set, color mode must not
  be set from HandleHDR but DPPS must be disabled.
- SetColorMode SDM Interface must be allowed to set the ColorMode
  when sdm.disable_hdr_lut_gen is set.
- In HWCTonemapper check if there is a FB session before using.

Change-Id: Id2e836bbe19b81244b0a9cc39e3d89e184c14c43
Crs-fixed: 1114947
2 files changed