kbuild: Fix missing system calls check on mips.

Commit 5f7efb4 (Kbuild: append missing-syscalls to the default target
list) broke MIPS build.

Reported-tested-and-acked-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: David Daney <david.daney@cavium.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>
diff --git a/arch/mips/Makefile b/arch/mips/Makefile
index 9b4cb00..0be3186 100644
--- a/arch/mips/Makefile
+++ b/arch/mips/Makefile
@@ -286,11 +286,11 @@
 archprepare:
 ifdef CONFIG_MIPS32_N32
 	@echo '  Checking missing-syscalls for N32'
-	$(Q)$(MAKE) $(build)=. missing-syscalls ccflags-y="-mabi=n32"
+	$(Q)$(MAKE) $(build)=. missing-syscalls missing_syscalls_flags="-mabi=n32"
 endif
 ifdef CONFIG_MIPS32_O32
 	@echo '  Checking missing-syscalls for O32'
-	$(Q)$(MAKE) $(build)=. missing-syscalls ccflags-y="-mabi=32"
+	$(Q)$(MAKE) $(build)=. missing-syscalls missing_syscalls_flags="-mabi=32"
 endif
 
 install: