package/Makefile.in: remove unused STRIP_STRIP_ALL variable

This variable has been unused for a long time, so we can get rid of its
definition.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/Makefile.in

@@ -203,7 +203,6 @@ TARGET_OBJDUMP  = $(TARGET_CROSS)objdump
 
 ifeq ($(BR2_STRIP_strip),y)
 STRIP_STRIP_DEBUG := --strip-debug
-STRIP_STRIP_ALL := --strip-all
 TARGET_STRIP = $(TARGET_CROSS)strip
 STRIPCMD = $(TARGET_CROSS)strip --remove-section=.comment --remove-section=.note
 endif