drm/i915: edp resume/On time optimization.

Make resume/on codepath not to wait for panel_power_cycle_delay(t11_t12)
if this time is already spent in suspend/poweron time.

v2: Use CLOCK_BOOTTIME and remove jiffies for panel power cycle
    delay calculation(Ville).

v3: Addressed below comments
    1. Tracking time from where last powercycle is initiated.
    2. Used ktime_get_bootime() wrapper for boottime clock.
    3. Used ktime_ms_delta() to get time difference.

v4: Updated v3 change log in detail.

v5: Removed static from panel_power_on_time(Stéphane).

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Abhay Kumar <abhay.kumar@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1453513144-14135-1-git-send-email-abhay.kumar@intel.com