fbdev: neofb: Shorten Neomagic product name in info struct

Avoid those compiler warnings:
neofb.c:1959:3: warning: 'snprintf' will always be truncated;
   specified size is 16, but format string expands to at least 17 [-Wfortify-source]

Signed-off-by: Helge Deller <deller@gmx.de>
Reported-by: Nathan Chancellor <nathan@kernel.org>
Reported-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Link: https://lore.kernel.org/all/CAKwvOdn0xoVWjQ6ufM_rojtKb0f1i1hW-J_xYGfKDNFdHwaeHQ@mail.gmail.com/
Link: https://github.com/ClangBuiltLinux/linux/issues/1923