bionic: Have putchar() put \r if \n is printed

Since putchar() is only called by printf() (as opposed to the lower-
level serial_putc()), we can have it nicely format the output by
adding \r when \n is printed.

To get the old behavior back, call serial_putc() directly.

This fixes gcc's optimization when calling:

    printf("\n")

As this will get silently turned into a call to putchar('\n')

Signed-off-by: Sean Cross <xobs@kosagi.com>

bionic.c

@@ -345,13 +345,14 @@ void _msleep(uint32_t msecs)
 int puts(const char *str)
 {
 	serial_puts(str);
-	serial_putc('\r');
 	serial_putc('\n');
 	return 1;
 }
 
 int putchar(int c)
 {
+	if (c == '\n')
+		serial_putc('\r');
 	serial_putc(c);
 	return c;
 }