fixup general __syscall breakage introduced in x32 port

the reordering of headers caused some risc archs to not see
the __syscall declaration anymore.
this caused build errors on mips with any compiler,
and on arm and microblaze with clang.

we now declare it locally just like the powerpc port does.

arch/arm/syscall_arch.h

@@ -3,6 +3,8 @@
 ((union { long long ll; long l[2]; }){ .ll = x }).l[1]
 #define __SYSCALL_LL_O(x) 0, __SYSCALL_LL_E((x))
 
+long (__syscall)(long, ...);
+
 #ifndef __clang__
 
 #define __asm_syscall(...) do { \

arch/microblaze/syscall_arch.h

@@ -3,6 +3,8 @@
 ((union { long long ll; long l[2]; }){ .ll = x }).l[1]
 #define __SYSCALL_LL_O(x) 0, __SYSCALL_LL_E((x))
 
+long (__syscall)(long, ...);
+
 #ifndef __clang__
 
 static __inline long __syscall0(long n)

arch/mips/syscall_arch.h

@@ -3,6 +3,8 @@
 ((union { long long ll; long l[2]; }){ .ll = x }).l[1]
 #define __SYSCALL_LL_O(x) 0, __SYSCALL_LL_E((x))
 
+long (__syscall)(long, ...);
+
 #ifndef __clang__
 
 #define __asm_syscall(...) do { \