printk: Remove no longer used second struct cont

If CONFIG_PRINTK=n:

    kernel/printk/printk.c:1893: warning: ‘cont’ defined but not used

Note that there are actually two different struct cont definitions and
objects: the first one is used if CONFIG_PRINTK=y, the second one became
unused by removing console_cont_flush().

Fixes: 5c2992ee7f ("printk: remove console flushing special cases for partial buffered lines")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Petr Mladek <pmladek@suse.com>
[ I do the occasional "allnoconfig" builds, but apparently not often
  enough  - Linus ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/printk/printk.c

@@ -1885,12 +1885,6 @@ static u32 console_idx;
 static u64 log_first_seq;
 static u32 log_first_idx;
 static u64 log_next_seq;
-static struct cont {
-	size_t len;
-	size_t cons;
-	u8 level;
-	bool flushed:1;
-} cont;
 static char *log_text(const struct printk_log *msg) { return NULL; }
 static char *log_dict(const struct printk_log *msg) { return NULL; }
 static struct printk_log *log_from_idx(u32 idx) { return NULL; }