drm/bridge: anx7625: Propagate errors from sp_tx_edid_read()

During the sp_tx_edid_read() call the return value of sp_tx_edid_read()
is ignored, which could cause potential errors to go unhandled.

All errors which are returned by sp_tx_edid_read() are handled in
anx7625_get_edid().

Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210818171318.1848272-2-robert.foss@linaro.org