drm/i915: Add PSR2 selective fetch registers

This registers will be used to implement PSR2 manual tracking/selective
fetch.

v2:
- Fixed typo in _PLANE_SEL_FETCH_BASE
- Renamed PSR2_MAN_TRK_CTL bits to better match spec names
- Renamed _PLANE_SEL_FETCH_* to better match spec names

BSpec: 55229
BSpec: 50424
BSpec: 50420
Cc: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200626010151.221388-3-jose.souza@intel.com