cosmetic: replace MIN, MAX with min, max

The macro MIN, MAX is defined as the aliase of min, max,
respectively.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
diff --git a/drivers/serial/usbtty.c b/drivers/serial/usbtty.c
index b030526..7fb0b92 100644
--- a/drivers/serial/usbtty.c
+++ b/drivers/serial/usbtty.c
@@ -475,7 +475,7 @@
 		if (space) {
 			write_buffer (&usbtty_output);
 
-			n = MIN (space, MIN (len, maxlen));
+			n = min(space, min(len, maxlen));
 			buf_push (&usbtty_output, str, n);
 
 			str += n;
@@ -882,7 +882,7 @@
 			space_avail =
 				current_urb->buffer_length -
 				current_urb->actual_length;
-			popnum = MIN (space_avail, buf->size);
+			popnum = min(space_avail, buf->size);
 			if (popnum == 0)
 				break;