s390: remove WARN_DYNAMIC_STACK

s390 is the only architecture which allows to set the
-mwarn-dynamicstack compile option. This however will also always
generate a warning with system call stack randomization, which uses
alloca to generate some random sized stack frame.

On the other hand Linus just enabled "-Werror" by default with commit
3fe617cc ("Enable '-Werror' by default for all kernel builds"),
which means compiles will always fail by default.

So instead of playing once again whack-a-mole for something which is
s390 specific, simply remove this option.
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

arch/s390/Kconfig

@@ -685,16 +685,6 @@ config STACK_GUARD
 	  The minimum size for the stack guard should be 256 for 31 bit and
 	  512 for 64 bit.
 
-config WARN_DYNAMIC_STACK
-	def_bool n
-	prompt "Emit compiler warnings for function with dynamic stack usage"
-	help
-	  This option enables the compiler option -mwarn-dynamicstack. If the
-	  compiler supports this options generates warnings for functions
-	  that dynamically allocate stack space using alloca.
-
-	  Say N if you are unsure.
-
 endmenu
 
 menu "I/O subsystem"

arch/s390/Makefile

@@ -85,13 +85,6 @@ cflags-$(CONFIG_CHECK_STACK) += -mstack-guard=$(CONFIG_STACK_GUARD)
 endif
 endif
 
-ifdef CONFIG_WARN_DYNAMIC_STACK
-  ifneq ($(call cc-option,-mwarn-dynamicstack),)
-    KBUILD_CFLAGS += -mwarn-dynamicstack
-    KBUILD_CFLAGS_DECOMPRESSOR += -mwarn-dynamicstack
-  endif
-endif
-
 ifdef CONFIG_EXPOLINE
   ifneq ($(call cc-option,$(CC_FLAGS_MARCH) -mindirect-branch=thunk),)
     CC_FLAGS_EXPOLINE := -mindirect-branch=thunk