drm/amd/display: Find first CRTC and its line time in dce110_fill_display_configs

dce110_fill_display_configs is shared between DCE 6-11, and
finding the first CRTC and its line time is relevant to DCE 6 too.
Move the code to find it from DCE 11 specific code.

Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Rodrigo Siqueira <siqueira@igalia.com>
Reviewed-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 4ab09785)
Cc: stable@vger.kernel.org