fbdev: stifb: Make the STI next font pointer a 32-bit signed offset

The pointer to the next STI font is actually a signed 32-bit
offset. With this change the 64-bit kernel will correctly subract
the (signed 32-bit) offset instead of adding a (unsigned 32-bit)
offset. It has no effect on 32-bit kernels.

This fixes the stifb driver with a 64-bit kernel on qemu.

Signed-off-by: Helge Deller <deller@gmx.de>
Cc: stable@vger.kernel.org

include/video/sticore.h

@@ -232,7 +232,7 @@ struct sti_rom_font {
 	 u8 height;
 	 u8 font_type;		/* language type */
 	 u8 bytes_per_char;
-	u32 next_font;
+	s32 next_font;		/* note: signed int */
 	 u8 underline_height;
 	 u8 underline_pos;
 	 u8 res008[2];