hush: complete renaming CONFIG_SYS_HUSH_PARSER to CONFIG_HUSH_PARSER

There is no more define of CONFIG_SYS_HUSH_PARSER.  Rename some
remaining references and drop the backward compatible Kconfig entry.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

cmd/Kconfig

@@ -13,7 +13,6 @@ config CMDLINE
 
 config HUSH_PARSER
 	bool "Use hush shell"
-	select SYS_HUSH_PARSER
 	depends on CMDLINE
 	help
 	  This option enables the "hush" shell (from Busybox) as command line
@@ -24,11 +23,6 @@ config HUSH_PARSER
 	  If disabled, you get the old, much simpler behaviour with a somewhat
 	  smaller memory footprint.
 
-config SYS_HUSH_PARSER
-	bool
-	help
-	  Backward compatibility.
-
 config SYS_PROMPT
 	string "Shell prompt"
 	default "=> "