fbcon: Add fbcon_rotate_hint to struct fb_info

On some hardware the LCD panel is not mounted upright in the casing,
but upside-down or rotated 90 degrees. In this case we want the console
to automatically be rotated to compensate.

The fbdev-driver may know about the need to rotate. Add a new
fbcon_rotate_hint field to struct fb_info, which gets initialized to -1.
If the fbdev-driver knows that some sort of rotation is necessary then
it can set this field to a FB_ROTATE_* value to tell the fbcon console
driver to rotate the console.

Acked-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171125193553.23986-2-hdegoede@redhat.com