kbuild: remove warning about "make depend"

Enough time has passed since "make depend" was deprecated.
Nobody would be in trouble without this hint.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>
diff --git a/Makefile b/Makefile
index 9fab639..d3726e5 100644
--- a/Makefile
+++ b/Makefile
@@ -1026,12 +1026,6 @@
 	$(srctree)/scripts/headerdep.pl -I$(srctree)/include
 
 # ---------------------------------------------------------------------------
-
-PHONY += depend dep
-depend dep:
-	@echo '*** Warning: make $@ is unnecessary now.'
-
-# ---------------------------------------------------------------------------
 # Firmware install
 INSTALL_FW_PATH=$(INSTALL_MOD_PATH)/lib/firmware
 export INSTALL_FW_PATH