drm/i915/glk: Set DCC delay range 2 in PLL enable sequence

Follow the PLL enable sequence updated in bspec, which requires the DCC
delay range 2 bit to be set.

v2: Moved from DDI init sequence to PLL enable.
v3: Don't read value from GRP register. (Rodrido)

Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Ander Conselvan De Oliveira <ander.conselvan.de.oliveira@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1480667037-11215-5-git-send-email-ander.conselvan.de.oliveira@intel.com