Add CONFIG_POST_UART to implement a board specific UART POST test.
This is done since lwmon5 needs to set POST_ALWAYS to run this
test on each reboot. And we don't want to change the default
behavious of this this.
Signed-off-by: Stefan Roese <sr@denx.de>
 #define CONFIG_SYS_POST_UART_TABLE     { CONFIG_SYS_NS16550_COM1, \
                        CONFIG_SYS_NS16550_COM2 }
 
+#define CONFIG_POST_UART  {                            \
+       "UART test",                                    \
+       "uart",                                         \
+       "This test verifies the UART operation.",       \
+       POST_RAM | POST_SLOWTEST | POST_ALWAYS | POST_MANUAL,   \
+       &uart_post_test,                                \
+       NULL,                                           \
+       NULL,                                           \
+       CONFIG_SYS_POST_UART                            \
+       }
+
 #define CONFIG_POST_WATCHDOG  {                                \
        "Watchdog timer test",                          \
        "watchdog",                                     \
 
     },
 #endif
 #if CONFIG_POST & CONFIG_SYS_POST_UART
+#if defined(CONFIG_POST_UART)
+       CONFIG_POST_UART,
+#else
     {
        "UART test",
        "uart",
        NULL,
        CONFIG_SYS_POST_UART
     },
+#endif /* CONFIG_POST_UART */
 #endif
 #if CONFIG_POST & CONFIG_SYS_POST_ETHER
     {