sh: mach-sh7763rdp: Assign FB_MODE_IS_UNKNOWN to struct fb_videomode.flag

sh: mach-sh7763rdp: Assign FB_MODE_IS_UNKNOWN to struct fb_videomode.flag

Assign FB_MODE_IS_UNKNOWN to sh7763fb_videomode.flag instead of
FBINFO_FLAG_DEFAULT. Both are 0, so the stored value does not change.

FBINFO_FLAG_DEFAULT is a flag for a framebuffer in struct fb_info.
Flags for videomodes are prefixed with FB_MODE_.

v3:
	* include board name in commit message (Adrian)
v2:
	* assign FB_MODE_IS_UNKNOWN (Adrian)

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Rich Felker <dalias@libc.org>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20230715185343.7193-9-tzimmermann@suse.de