core: change the strip command from a choice to a boolean

Curently, we have a choice to select between stripping and not
stripping. This is legacy code from back when we had a third option,
sstrip (super-strip).

Since we removed sstrip, stripping or not stripping is now just a
boolean rather than a choice.

Make it so.

We make BR2_STRIP_strip default to 'y' to keep the current behaviour of
defaulting to stripping.

Move BR2_STIP_none to legacy, and instruct the user to review the new
setting.

Drop any reference to BR2_STRIP_none in comments.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Arnout Vandecappelle <arnout@mind.be>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

Config.in

@@ -414,13 +414,10 @@ config BR2_DEBUG_3
 endchoice
 endif
 
-choice
-	prompt "strip command for binaries on target"
-	default BR2_STRIP_strip
-
 config BR2_STRIP_strip
-	bool "strip"
+	bool "strip target binaries"
 	depends on !BR2_PACKAGE_HOST_ELF2FLT
+	default y
 	help
 	  Binaries and libraries in the target filesystem will be
 	  stripped using the normal 'strip' command. This allows to save
@@ -428,12 +425,6 @@ config BR2_STRIP_strip
 	  on the target are needed for native debugging, but not when
 	  remote debugging is used.
 
-config BR2_STRIP_none
-	bool "none"
-	help
-	  Do not strip binaries and libraries in the target filesystem.
-endchoice
-
 config BR2_STRIP_EXCLUDE_FILES
 	string "executables that should not be stripped"
 	depends on BR2_STRIP_strip