serial: pl011: Resend the character if FIFO is full in debug uart

pl01x_putc() might return -EAGAIN if there was no space in FIFO. In that
case, high-level caller should wait until there is space and resend the
character.

Signed-off-by: Chen Baozi <chenbaozi@phytium.com.cn>
Reviewed-by: Stefan Roese <sr@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>

drivers/serial/serial_pl01x.c

@@ -417,7 +417,8 @@ static inline void _debug_uart_putc(int ch)
 {
 	struct pl01x_regs *regs = (struct pl01x_regs *)CONFIG_DEBUG_UART_BASE;
 
-	pl01x_putc(regs, ch);
+	while (pl01x_putc(regs, ch) == -EAGAIN)
+		;
 }
 
 DEBUG_UART_FUNCS