drm/i915/psr: Fix PSR_IMR/IIR field handling

Current PSR code is supposed to use TRANSCODER_EDP to force 0 shift for
bits in PSR_IMR/IIR registers:

/*
 * gen12+ has registers relative to transcoder and one per transcoder
 * using the same bit definition: handle it as TRANSCODER_EDP to force
 * 0 shift in bit definition
 */

At the time of writing the code assumption "TRANSCODER_EDP == 0" was made.
This is not the case and all fields in PSR_IMR and PSR_IIR are shifted
incorrectly if DISPLAY_VER >= 12.

Fix this by adding separate register field defines for >=12 and add bit
getter functions to keep code readability.

v4:
 - Remove EDP from TGL definitions (José)
 - Use REG_BIT and REG_GENMASK (José)
v3:
 - Add separate register field defines (José)
 - Add bit getter functions (José)
v2:
 - Improve commit message (José)

Cc: José Roberto de Souza <jose.souza@intel.com>
Cc: Mika Kahola <mika.kahola@intel.com>

Fixes: 8241cfbe ("drm/i915/tgl: Access the right register when handling PSR interruptions")
Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221003072011.72408-1-jouni.hogander@intel.com