drm/amd/display: Skip checking FRL_MODE bit for PCON BW determination

[Why/How]
Certain PCON will clear the FRL_MODE bit despite supporting the link BW
indicated in the other bits.

Thus, skip checking the FRL_MODE bit when interpreting the
hdmi_encoded_link_bw struct.

Reviewed-by: Wenjing Liu <wenjing.liu@amd.com>
Signed-off-by: George Shen <george.shen@amd.com>
Signed-off-by: Wayne Lin <wayne.lin@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>