vsprintf: reduce code size by avoiding extra check

No functional change, just refactor the code so that it avoid checking
"if (hi)" two times in a sequence, taking advantage of previous check made.

It also reduces code size:
   text    data     bss     dec     hex filename
  15726       0       8   15734    3d76 vsprintf.o (ex lib/lib.a-BEFORE)
  15710       0       8   15718    3d66 vsprintf.o (ex lib/lib.a-AFTER)
Signed-off-by: André Goddard Rosa <andre.goddard@gmail.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/vsprintf.c

@@ -797,8 +797,9 @@ static char *ip6_compressed_string(char *p, const char *addr)
 				p = pack_hex_byte(p, hi);
 			else
 				*p++ = hex_asc_lo(hi);
+			p = pack_hex_byte(p, lo);
 		}
-		if (hi || lo > 0x0f)
+		else if (lo > 0x0f)
 			p = pack_hex_byte(p, lo);
 		else
 			*p++ = hex_asc_lo(lo);