If the source of the backlight PWM is from the
panel then the PWM can be controlled by DCS
command, this patch adds the support to
enable/disbale panel PWM, control backlight level
etc...

v2: Moving the CABC bkl functions to new file.(Jani)

v3: Rebase

v4: Rebase

v5: Use mipi_dsi_dcs_write() instead of mipi_dsi_dcs_write_buffer() (Jani)
    Move DCS macro`s to include/video/mipi_display.h (Jani)

v6: Rename the file to intel_dsi_panel_pwm.c
    Removing the CABC operations

v7 by Jani: renames, rebases, etc.

v8 by Jani: s/INTEL_BACKLIGHT_CABC/INTEL_BACKLIGHT_DSI_DCS/

v9 by Jani: rename init function to intel_dsi_dcs_init_backlight_funcs

Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: Yetunde Adebisi <yetundex.adebisi@intel.com>
Signed-off-by: Deepak M <m.deepak@intel.com>
Reviewed-by: Yetunde Adebisi <yetundex.adebisi@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/71238a4b14b8c3a6c04070c789f09f1b4bc00a15.1461676337.git.jani.nikula@intel.com