Makefile: Silence the deprecation script

This bash code is currently showing up in the build unless 'make -s' is
used. We don't normally show these sorts of things as they are confusing.
Also this code was not shown before the recent refactoring of how these
messages are displayed.

Add an '@' to silence it.
Suggested-by: NTom Rini <trini@konsulko.com>
Signed-off-by: NSimon Glass <sjg@chromium.org>
Reported-by: NBin Meng <bmeng.cn@gmail.com>
Fixes: 13732528 ("Makefile: Add common code to report deprecation")

Makefile

@@ -1027,7 +1027,7 @@ expect = $(foreach cfg,$(1),y)
 # Note: Script avoids bash construct, hence the strange double 'if'
 # (patches welcome!)
 define deprecated
-	if [ -n "$(strip $(4))" ]; then if [ "$(got)" != "$(expect)" ]; then \
+	@if [ -n "$(strip $(4))" ]; then if [ "$(got)" != "$(expect)" ]; then \
 		echo >&2 "===================== WARNING ======================"; \
 		echo >&2 "This board does not use $(firstword $(1)) (Driver Model"; \
 		echo >&2 "for $(2)). Please update the board to use"; \