82xx serial, smc: add configurable SMC Rx buffer len

This patch adds the configuration option CONFIG_SYS_SMC_RXBUFLEN.
With this option it is possible to allow the receive
buffer for the SMC on 82xx to be greater then 1. In case
CONFIG_SYS_SMC_RXBUFLEN == 1 this driver works as the
old version.

When defining CONFIG_SYS_SMC_RXBUFLEN also
CONFIG_SYS_MAXIDLE must be defined to setup the maximum
idle timeout for the SMC.

Signed-off-by: Heiko Schocher <hs@denx.de>
diff --git a/README b/README
index 522471c..fcadf3f 100644
--- a/README
+++ b/README
@@ -484,6 +484,14 @@
 		CONFIG_SYS_BAUDRATE_TABLE, see below.
 		CONFIG_SYS_BRGCLK_PRESCALE, baudrate prescale
 
+- Console Rx buffer length
+		With CONFIG_SYS_SMC_RXBUFLEN it is possible to define
+		the maximum receive buffer length for the SMC.
+		This option is actual only for 82xx possible.
+		If using CONFIG_SYS_SMC_RXBUFLEN also CONFIG_SYS_MAXIDLE
+		must be defined, to setup the maximum idle timeout for
+		the SMC.
+
 - Interrupt driven serial port input:
 		CONFIG_SERIAL_SOFTWARE_FIFO