kbuild: kill do_cmd

The lonely two users of do_cmd has gone.
Therefore we can now kill it for good

scripts/Makefile.lib

@@ -220,24 +220,6 @@ if_changed_rule = $(if $(strip $? \
 
 cmd = @$(if $($(quiet)cmd_$(1)),echo '  $($(quiet)cmd_$(1))' &&) $(cmd_$(1))
 
-# do_cmd is a shorthand used to support both compressed, verbose
-# and silent output in a single line.
-# Compared to cmd described avobe, do_cmd does no rely on any variables 
-# previously assigned a value.
-#
-# Usage $(call do_cmd,CMD   $@,cmd_to_execute bla bla)
-# Example:
-# $(call do_cmd,CP $@,cp -b $< $@)
-# make -s => nothing will be printed
-# make KBUILD_VERBOSE=1 => cp -b path/to/src.file path/to/dest.file
-# make KBUILD_VERBOSE=0 =>   CP path/to/dest.file
-define do_cmd
-	@$(if $(filter quiet_,$(quiet)), echo '  $(1)' &&,
-           $(if $(filter silent_,$(quiet)),,
-             echo "$(2)" &&)) \
-        $(2)
-endef
-
 #	$(call descend,<dir>,<target>)
 #	Recursively call a sub-make in <dir> with target <target> 
 # Usage is deprecated, because make do not see this as an invocation of make.