drm/amd/display: Fix bounds check for dcn35 DcfClocks

[Why]
NumFclkLevelsEnabled is used for DcfClocks bounds check
instead of designated NumDcfClkLevelsEnabled.
That can cause array index out-of-bounds access.

[How]
Use designated variable for dcn35 DcfClocks bounds check.

Fixes: a8edc9cc ("drm/amd/display: Fix array-index-out-of-bounds in dcn35_clkmgr")
Cc: Mario Limonciello <mario.limonciello@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Reviewed-by: Sun peng Li <sunpeng.li@amd.com>
Acked-by: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Roman Li <roman.li@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>