[klibc] fwrite: fix the implementation of _IONBF

The _IONBF implementation was a duplicate of _IOFBF, which is
obviously incorrect.  Actually make sure we flush after each write.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
diff --git a/usr/klibc/stdio/fwrite.c b/usr/klibc/stdio/fwrite.c
index d167257..5d2c3f0 100644
--- a/usr/klibc/stdio/fwrite.c
+++ b/usr/klibc/stdio/fwrite.c
@@ -82,8 +82,8 @@
 
 	case _IONBF:
 	default:
-		pf_len = 0;
-		pu_len = count;
+		pf_len = count;
+		pu_len = 0;
 		break;
 	}