mx6slevk: Use the default CONFIG_SYS_PBSIZE

Entering the maximum number of characters defined by CONFIG_SYS_CBSIZE into
the console and hitting enter afterwards, causes a hang in the system because
CONFIG_SYS_PBSIZE is not capable of storing the extra characters of the error
message:
"Unknown command '' - try 'help'".

Use the default CONFIG_SYS_PBSIZE definition from config_fallbacks.h to solve
this problem.

Cc: Jason Liu <r64343@freescale.com>
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Acked-by: Jason Liu <r64343@freescale.com>
diff --git a/include/configs/mx6slevk.h b/include/configs/mx6slevk.h
index 1221418..21c654b 100644
--- a/include/configs/mx6slevk.h
+++ b/include/configs/mx6slevk.h
@@ -169,8 +169,6 @@
 #define CONFIG_AUTO_COMPLETE
 #define CONFIG_SYS_CBSIZE		256
 
-/* Print Buffer Size */
-#define CONFIG_SYS_PBSIZE (CONFIG_SYS_CBSIZE + sizeof(CONFIG_SYS_PROMPT) + 16)
 #define CONFIG_SYS_MAXARGS		16
 #define CONFIG_SYS_BARGSIZE CONFIG_SYS_CBSIZE