drm/modes: parse_cmdline: Remove some unnecessary code (v2)

fb_get_options() will return fb_mode_option if no video=<connector-name>
argument is present on the kernel commandline, so there is no need to also
do this in drm_mode_parse_command_line_for_connector() as our only caller
uses fb_get_options() to get the mode_option argument.

Changes in v2:
-Split out the changes dealing with the initialization of the mode struct
 into a separate patch

Acked-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191118155134.30468-10-hdegoede@redhat.com