drm/i915/bxt: Reject DMC firmware versions with known bugs

DMC version 1.06 has a known bug, where the firmware polls forever for a
port PLL to lock, if the PLL was disabled when entering DC5, which locks
up the machine. Version 1.07 fixes this, so make that the minimum
required version on BXT.

CC: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1459515767-29228-2-git-send-email-imre.deak@intel.com