Convert CONFIG_SYS_PBSIZE to Kconfig

This converts the following to Kconfig:
   CONFIG_SYS_PBSIZE

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/cmd/Kconfig b/cmd/Kconfig
index dd43358..b50e53e 100644
--- a/cmd/Kconfig
+++ b/cmd/Kconfig
@@ -75,6 +75,10 @@
 	int "Maximum number arguments accepted by commands"
 	default 16
 
+config SYS_PBSIZE
+	int "Buffer size for console output"
+	default 1044
+
 config SYS_XTRACE
 	bool "Command execution tracer"
 	depends on CMDLINE