drm/amd/display: Cleanup PSR flag

[Why]
enable_sw_cntl_psr flag is not needed.
For PSR1 and PSR2, we should be passing
dirty rectangle and cursor updates to FW
regardless of enable_sw_cntl_psr flag.

[How]
Remove enable_sw_cntl_psr flag from driver.
Send cursor info and dirty rectagle status to
dmub only in the case of dcn31 and above.

Reviewed-by: Anthony Koo <Anthony.Koo@amd.com>
Reviewed-by: Robin Chen <robin.chen@amd.com>
Acked-by: Brian Chang <Brian.Chang@amd.com>
Signed-off-by: Gabe Teeger <gabe.teeger@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>