vt: Store font in struct vc_font

vt: Store font in struct vc_font

Replace struct console_font with struct vc_font for the type of the
vc_font field of struct vc_data. Struct console_font is UAPI, which
prevents further changes. Hence a new data type is required.

Struct console_font has a documented vertical pitch of 32 bytes. This
is not the case after the font data has been loaded into the kernel.
Changing the type of vc_font addresses this inconsistency.

The font data is now declared as constant, as it might come from the
kernel's read-only section. There's some fallout throughout the console
code where non-const variables refer to it. Fix them. A later update
will declare the font data to a dedicated data type.

v3:
- fix typos

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Helge Deller <deller@gmx.de>