Olof reports that noMMU builds error out with:
arch/arm/kernel/signal.c: In function 'setup_return':
arch/arm/kernel/signal.c:413:25: error: 'mm_context_t' has no member named 'sigpage'
This shows one of the evilnesses of IS_ENABLED().  Get rid of it here
and replace it with #ifdef's - and as no noMMU platform can make use
of sigpage, depend on CONIFG_MMU not CONFIG_ARM_MPU.
Reported-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
 extern unsigned long arch_randomize_brk(struct mm_struct *mm);
 #define arch_randomize_brk arch_randomize_brk
 
+#ifdef CONFIG_MMU
 #define ARCH_HAS_SETUP_ADDITIONAL_PAGES 1
 struct linux_binprm;
 int arch_setup_additional_pages(struct linux_binprm *, int);
+#endif
 
 #endif
 
                    __put_user(sigreturn_codes[idx+1], rc+1))
                        return 1;
 
-               if ((cpsr & MODE32_BIT) && !IS_ENABLED(CONFIG_ARM_MPU)) {
+#ifdef CONFIG_MMU
+               if (cpsr & MODE32_BIT) {
                        struct mm_struct *mm = current->mm;
 
                        /*
                         */
                        retcode = mm->context.sigpage + signal_return_offset +
                                  (idx << 2) + thumb;
-               } else {
+               } else
+#endif
+               {
                        /*
                         * Ensure that the instruction cache sees
                         * the return code written onto the stack.