cmd: Kconfig: migrate CONFIG_SYS_PROMPT_HUSH_PS2

Move CONFIG_SYS_PROMPT_HUSH_PS2 in Kconfig, depending
on CONFIG_HUSH_PARSER, and remove the default value defined
in cli_hush.c under __U_BOOT__.

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/cmd/Kconfig b/cmd/Kconfig
index 1595de9..98cf543 100644
--- a/cmd/Kconfig
+++ b/cmd/Kconfig
@@ -55,6 +55,15 @@
 	  This string is displayed in the command line to the left of the
 	  cursor.
 
+config SYS_PROMPT_HUSH_PS2
+	string "Hush shell secondary prompt"
+	depends on HUSH_PARSER
+	default "> "
+	help
+	  This defines the secondary prompt string, which is
+	  printed when the command interpreter needs more input
+	  to complete a command. Usually "> ".
+
 config SYS_XTRACE
 	string "Command execution tracer"
 	depends on CMDLINE