drm/amd/display: fix potential infinite loop in fbc path

- Fixing integer overflow bug in wait_for_fbc_state_changed()
- Correct the max value of retries for the corresponding warning

Signed-off-by: Roman Li <Roman.Li@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>