s390: remove ARCH_SELECT_MEMORY_MODEL

The only reason s390 has ARCH_SELECT_MEMORY_MODEL option in
arch/s390/Kconfig is an ancient compile error with allnoconfig which was
fixed by commit 97195d6b ("[S390] fix sparsemem related compile error
with allnoconfig on s390") by adding the ARCH_SELECT_MEMORY_MODEL option.

Since then a lot have changed and now allnoconfig builds just fine without
ARCH_SELECT_MEMORY_MODEL, so it can be removed.

Link: http://lkml.kernel.org/r/1556740577-4140-3-git-send-email-rppt@linux.ibm.comSigned-off-by: NMike Rapoport <rppt@linux.ibm.com>
Acked-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Russell King <linux@armlinux.org.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

arch/s390/Kconfig

@@ -641,9 +641,6 @@ config ARCH_SPARSEMEM_ENABLE
 config ARCH_SPARSEMEM_DEFAULT
 	def_bool y
 
-config ARCH_SELECT_MEMORY_MODEL
-	def_bool y
-
 config ARCH_ENABLE_MEMORY_HOTPLUG
 	def_bool y if SPARSEMEM