drm/i915/debugfs: Print PSR selective update status register values

The value of this registers will be used to test if PSR2 is doing
selective update and if the number of blocks match with the expected.

v2:
- Using new macros
- Changed the string output

v3:
- reading PSR2_SU_STATUS registers together(Dhinakaran)
- printing SU blocks of frames with 0 updates(Dhinakaran)

Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Reviewed-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190117205548.28378-4-jose.souza@intel.com