drm/i915/dp: No need to poll FEC Enable Live bit

The Bspec does not mention polling the FEC Enable
Live status bit. That is only there for debug purposes.
So remove the polling from driver.

Cc: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201125072634.27664-1-manasi.d.navare@intel.com