kbuild: remove duplicated comments about PHONY

The comment is the same as in the top-level Makefile.

Also, the comments contain typos:
  - the .PHONY variable  ->  the PHONY variable
  - se we can ...        ->  so we can ...

Instead of fixing the typos, just remove the duplicated comments.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

scripts/Makefile.build

@@ -590,7 +590,4 @@ endif
 # We never want them to be removed automatically.
 .SECONDARY: $(targets)
 
-# Declare the contents of the .PHONY variable as phony.  We keep that
-# information in a variable se we can use it in if_changed and friends.
-
 .PHONY: $(PHONY)

scripts/Makefile.clean

@@ -88,7 +88,4 @@ PHONY += $(subdir-ymn)
 $(subdir-ymn):
 	$(Q)$(MAKE) $(clean)=$@
 
-# Declare the contents of the .PHONY variable as phony.  We keep that
-# information in a variable se we can use it in if_changed and friends.
-
 .PHONY: $(PHONY)

scripts/Makefile.modbuiltin

@@ -54,8 +54,4 @@ PHONY += $(subdir-ym)
 $(subdir-ym):
 	$(Q)$(MAKE) $(modbuiltin)=$@
 
-
-# Declare the contents of the .PHONY variable as phony.  We keep that
-# information in a variable se we can use it in if_changed and friends.
-
 .PHONY: $(PHONY)

scripts/Makefile.modinst

@@ -35,8 +35,4 @@ modinst_dir = $(if $(KBUILD_EXTMOD),$(ext-mod-dir),kernel/$(@D))
 $(modules):
 	$(call cmd,modules_install,$(MODLIB)/$(modinst_dir))
 
-
-# Declare the contents of the .PHONY variable as phony.  We keep that
-# information in a variable so we can use it in if_changed and friends.
-
 .PHONY: $(PHONY)

scripts/Makefile.modpost

@@ -149,8 +149,4 @@ ifneq ($(cmd_files),)
   include $(cmd_files)
 endif
 
-
-# Declare the contents of the .PHONY variable as phony.  We keep that
-# information in a variable se we can use it in if_changed and friends.
-
 .PHONY: $(PHONY)

scripts/Makefile.modsign

@@ -27,7 +27,4 @@ modinst_dir = $(if $(KBUILD_EXTMOD),$(ext-mod-dir),kernel/$(@D))
 $(modules):
 	$(call cmd,sign_ko,$(MODLIB)/$(modinst_dir))
 
-# Declare the contents of the .PHONY variable as phony.  We keep that
-# information in a variable se we can use it in if_changed and friends.
-
 .PHONY: $(PHONY)