Enable HW Default flip for small PL.

bspec: 52890
bspec: 53508
bspec: 53273

v2: rebase to drm-tip
v3: move from ctx to gt workarounds. Remove whitelist.
v4: move to rcs WA init

Cc: Matt Atwood <matthew.s.atwood@intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Cc: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: Clint Taylor <clinton.a.taylor@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200826025724.20944-1-clinton.a.taylor@intel.com