Revert "serial: ns16550: Add RX interrupt buffer support"

This reverts commit 6822cf3ec7.

As Bin Meng has tested and pointed out, we don't need the RX interrupt
for the RX buffer support at all. Just reading all available characters
into a buffer is sufficient to solve the problem with the dropped
characters upon long lines pasted into the U-Boot prompt. Since this
RX buffer support can be implemented in a generic way, without any
device specifica (e.g. for the ns16550), I'll post a new patch with
a new serial RX buffer support for DM, which all DM based serial
drivers can use.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Simon Glass <sjg@chromium.org>
Cc: Bin Meng <bmeng.cn@gmail.com>
Cc: Tom Rini <trini@konsulko.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

include/ns16550.h

@@ -51,10 +51,6 @@
  * @base:		Base register address
  * @reg_shift:		Shift size of registers (0=byte, 1=16bit, 2=32bit...)
  * @clock:		UART base clock speed in Hz
- *
- * @buf:		Pointer to the RX interrupt buffer
- * @rd_ptr:		Read pointer in the RX interrupt buffer
- * @wr_ptr:		Write pointer in the RX interrupt buffer
  */
 struct ns16550_platdata {
 	unsigned long base;
@@ -62,12 +58,6 @@ struct ns16550_platdata {
 	int clock;
 	int reg_offset;
 	u32 fcr;
-
-	int irq;
-
-	char *buf;
-	int rd_ptr;
-	int wr_ptr;
 };
 
 struct udevice;