Makefile: Remove 'quiet' variable

'quiet' variable is set and exported, but it is not used. We can safely
remove it.

This variable is inherited from the Makefile of the Linux kernel, and
is not used in Buildroot.

In support/scripts/mkmakefile, 'quiet' value is checked, but the test
is always true ('quiet' is never set to silent_), so the test can be
removed as well.

Signed-off-by: Cédric Marie <cedric.marie@openmailbox.org>
Reviewed-by: "James Knight" <james.d.knight@live.com>
Reviewed-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
diff --git a/Makefile b/Makefile
index dd8959f..8e3f657 100644
--- a/Makefile
+++ b/Makefile
@@ -228,14 +228,12 @@
 endif
 
 ifeq ($(KBUILD_VERBOSE),1)
-  quiet =
   Q =
 ifndef VERBOSE
   VERBOSE = 1
 endif
 export VERBOSE
 else
-  quiet = quiet_
   Q = @
 endif
 
@@ -247,7 +245,7 @@
 # kconfig uses CONFIG_SHELL
 CONFIG_SHELL := $(SHELL)
 
-export SHELL CONFIG_SHELL quiet Q KBUILD_VERBOSE
+export SHELL CONFIG_SHELL Q KBUILD_VERBOSE
 
 ifndef HOSTAR
 HOSTAR := ar