fix broken offset argument to the mmap2 syscall on or1k

for or1k, the kernel expects the offset passed to mmap2 in units of
the 8k page size, not the standard unit of 4k used on most other
archs.

arch/or1k/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))
 
+#define SYSCALL_MMAP2_UNIT 8192ULL
+
 long (__syscall)(long, ...);
 
 #ifndef __clang__