drm/i915/dp: Add debug messages to print DP link training pattern

Currently we do not print the training pattern used in any of the DP link
training stages. Including this piece of information in debug messages will
help debugging.

Also, use the wrapper intel_dp_program_link_training_pattern() in
intel_dp_enable_port() instead of implementing it.

v2: Downgraded log level from error to debug (Chris)

Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1470343716-5574-2-git-send-email-dhinakaran.pandiyan@intel.com