Create configuration option for restricted ns16550 functions

This patch will create a configuration option for a minimum configuration for
the ns16550 serial driver at drivers/serial/ns16550.c and will apply this new
configuration option to the SIMPC8313.h config file in order to fix the NAND
bootstrap build error.  This option will exclude all functions with exception of
NS16550_putc and NS16550_init.  This will be used primarily to save space and
remove unused code from builds in which space is limited.
Signed-off-by: NRon Madrid <ron_madrid@sbcglobal.net>

README

@@ -2458,6 +2458,13 @@ use the "saveenv" command to store a valid environment.
 - CONFIG_SYS_64BIT_STRTOUL:
 		Adds simple_strtoull that returns a 64bit value
 
+- CONFIG_NS16550_MIN_FUNCTIONS:
+		Define this if you desire to only have use of the NS16550_init
+		and NS16550_putc functions for the serial driver located at
+		drivers/serial/ns16550.c.  This option is useful for saving
+		space for already greatly restricted images, including but not
+		limited to NAND_SPL configurations.
+
 Low Level (hardware related) configuration options:
 ---------------------------------------------------
 

drivers/serial/ns16550.c

@@ -39,6 +39,7 @@ void NS16550_init (NS16550_t com_port, int baud_divisor)
 #endif
 }
 
+#ifndef CONFIG_NS16550_MIN_FUNCTIONS
 void NS16550_reinit (NS16550_t com_port, int baud_divisor)
 {
 	com_port->ier = 0x00;
@@ -53,6 +54,7 @@ void NS16550_reinit (NS16550_t com_port, int baud_divisor)
 	com_port->dlm = (baud_divisor >> 8) & 0xff;
 	com_port->lcr = LCRVAL;
 }
+#endif /* CONFIG_NS16550_MIN_FUNCTIONS */
 
 void NS16550_putc (NS16550_t com_port, char c)
 {
@@ -60,6 +62,7 @@ void NS16550_putc (NS16550_t com_port, char c)
 	com_port->thr = c;
 }
 
+#ifndef CONFIG_NS16550_MIN_FUNCTIONS
 char NS16550_getc (NS16550_t com_port)
 {
 	while ((com_port->lsr & LSR_DR) == 0) {
@@ -76,4 +79,5 @@ int NS16550_tstc (NS16550_t com_port)
 	return ((com_port->lsr & LSR_DR) != 0);
 }
 
+#endif /* CONFIG_NS16550_MIN_FUNCTIONS */
 #endif

include/configs/SIMPC8313.h

@@ -205,6 +205,9 @@
 #define CONFIG_SYS_NS16550
 #define CONFIG_SYS_NS16550_SERIAL
 #define CONFIG_SYS_NS16550_REG_SIZE	1
+#ifdef CONFIG_NAND_SPL
+#define CONFIG_NS16550_MIN_FUNCTIONS
+#endif
 
 #define CONFIG_SYS_BAUDRATE_TABLE	\
 	{300, 600, 1200, 2400, 4800, 9600, 19200, 38400, 115200}