drm/i915: Split bxt_ddi_pll_select()

Split out of bxt_ddi_pll_select() the logic that calculates the pll
dividers and dpll_hw_state into a new function that doesn't depend on
crtc state. This will be used for enabling the port pll when doing
upfront link training.

v2:
* Refactored code so that bxt_clk_div need not be exported (Durga)
v1:
* Rebased on top of intel_dpll_mgr.c (Durga)
* Initial version from Ander on top of intel_ddi.c

Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>
Signed-off-by: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Signed-off-by: Durgadoss R <durgadoss.r@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
diff --git a/drivers/gpu/drm/i915/intel_dpll_mgr.h b/drivers/gpu/drm/i915/intel_dpll_mgr.h
index 89c5ada..11a85a5 100644
--- a/drivers/gpu/drm/i915/intel_dpll_mgr.h
+++ b/drivers/gpu/drm/i915/intel_dpll_mgr.h
@@ -160,5 +160,8 @@
 void intel_shared_dpll_commit(struct drm_atomic_state *state);
 void intel_shared_dpll_init(struct drm_device *dev);
 
+/* BXT dpll related functions */
+bool bxt_ddi_dp_set_dpll_hw_state(int clock,
+			  struct intel_dpll_hw_state *dpll_hw_state);
 
 #endif /* _INTEL_DPLL_MGR_H_ */