drm/i915/skl+: Use plane size for relative data rate calculation

Use plane size for relative data rate calculation. don't always use
pipe source width & height.
adjust height & width according to rotation.
use plane size for watermark calculations also.

v2: Address Matt's comments.
    Use intel_plane_state->visible to avoid divide-by-zero error.
    Where FB was present but not visible so causing total data rate to
    be zero, hence divide-by-zero.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93917
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94044


Cc: drm-intel-fixes@lists.freedesktop.org
Signed-off-by: Kumar, Mahesh <mahesh1.kumar@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1459956399-1296-1-git-send-email-matthew.d.roper@intel.com