Fonts: Make font size unsigned in font_desc

`width` and `height` are defined as unsigned in our UAPI font descriptor
`struct console_font`. Make them unsigned in our kernel font descriptor
`struct font_desc`, too.

Also, change the corresponding printk() format identifiers from `%d` to
`%u`, in sti_select_fbfont().

Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20201028105647.1210161-1-yepeilin.cs@gmail.com