drm/i915/dsi: fix MIPI_BKLT_EN_1 native GPIO index

Due to copy-paste fail, MIPI_BKLT_EN_1 would always use PPS index 1,
never 0. Fix the sloppiest commit in recent memory.

Fixes: f087cfe6 ("drm/i915/dsi: add support for ICL+ native MIPI GPIO sequence")
Reported-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221220140105.313333-1-jani.nikula@intel.com