drm/amd/display: Add missing PSR state

[why]
PSR_STATE2b was introduced on DMCUB side, but not on the driver side,
which caused convert_psr_state helper function to return
PSR_STATE_INVALID. That caused visual lagging during state transition.

[how]
Add PSR_STATE2b to dc_psr_state and convert_psr_state
Reviewed-by: Wyatt Wood <Wyatt.Wood@amd.com>
Acked-by: Agustin Gutierrez Sanchez <agustin.gutierrez@amd.com>
Signed-off-by: Mikita Lipski <mikita.lipski@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dc_types.h

@@ -653,6 +653,7 @@ enum dc_psr_state {
 	PSR_STATE1a,
 	PSR_STATE2,
 	PSR_STATE2a,
+	PSR_STATE2b,
 	PSR_STATE3,
 	PSR_STATE3Init,
 	PSR_STATE4,

drivers/gpu/drm/amd/display/dc/dce/dmub_psr.c

@@ -50,6 +50,8 @@ static enum dc_psr_state convert_psr_state(uint32_t raw_state)
 		state = PSR_STATE2;
 	else if (raw_state == 0x21)
 		state = PSR_STATE2a;
+	else if (raw_state == 0x22)
+		state = PSR_STATE2b;
 	else if (raw_state == 0x30)
 		state = PSR_STATE3;
 	else if (raw_state == 0x31)