drm/i915/cnl: Fix loadgen select programming on ddi vswing sequence

The condition for setting the Loadgen Select bit of
PORT_TX_DW4 register during DDI Vswing Sequence should be
Bit rate <=6 GHz whereas the existing code checks only
Bit Rate < 6GHz. This patch fixes this condition.
While at it also remove the redundant paranthesis.

Fixes: cf54ca8b

 ("drm/i915/cnl: Implement voltage swing sequence.")
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1500329122-32662-1-git-send-email-manasi.d.navare@intel.com


Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
(cherry picked from commit a8e45a1c

)
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>