Introduce HAVE_AOUT symbol to remove hard-coded arch list for BINFMT_AOUT

HAVE_AOUT doesn't quite do the same thing as the recently removed
ARCH_SUPPORTS_AOUT config option. That was set even on platforms where
binfmt_aout isn't supported, although it's not entirely clear why.

So it's best just to introduce a new symbol, handled consistently with
other similar HAVE_xxx symbols; with a simple 'select' in the arch Kconfig.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
diff --git a/fs/Kconfig.binfmt b/fs/Kconfig.binfmt
index e4df913..17c9c5e 100644
--- a/fs/Kconfig.binfmt
+++ b/fs/Kconfig.binfmt
@@ -59,9 +59,12 @@
 	help
 	  Support FLAT shared libraries
 
+config HAVE_AOUT
+       def_bool n
+
 config BINFMT_AOUT
 	tristate "Kernel support for a.out and ECOFF binaries"
-	depends on (X86_32 || ALPHA || ARM || M68K)
+	depends on HAVE_AOUT
 	---help---
 	  A.out (Assembler.OUTput) is a set of formats for libraries and
 	  executables used in the earliest versions of UNIX.  Linux used