m68k: sun3: Remove unused vsprintf() return value in prom_printf()

When building with W=1:

arch/m68k/sun3/prom/printf.c: In function ‘prom_printf’:
arch/m68k/sun3/prom/printf.c:28:13: warning: variable ‘i’ set but not used [-Wunused-but-set-variable]
28 | int i;
| ^

As the return value of vsprintf() is unused, and serves no practical
purpose here, fix this by removing the variable.

Signed-off-by: Geert Uytterhoeven <[e-mail]>
Acked-by: Arnd Bergmann <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

arch/m68k/sun3/prom/printf.c

···
 {
 	va_list args;
 	char ch, *bptr;
-	int i;
 
 	va_start(args, fmt);
 
 #ifdef CONFIG_KGDB
 	ppbuf[0] = 'O';
-	i = vsprintf(ppbuf + 1, fmt, args) + 1;
+	vsprintf(ppbuf + 1, fmt, args) + 1;
 #else
-	i = vsprintf(ppbuf, fmt, args);
+	vsprintf(ppbuf, fmt, args);
 #endif
 
 	bptr = ppbuf;