Reserve x18 on AArch64 and un-reserve x16

Author: Amanieu

std/src/sys/sgx/ext/arch.rs

@@ -33,9 +33,9 @@ pub fn egetkey(request: &Align512<[u8; 512]>) -> Result<Align16<[u8; 16]>, u32>
 
         asm!(
             // rbx is reserved by LLVM
-            "xchg {}, rbx",
+            "xchg {0}, rbx",
             "enclu",
-            "mov rbx, {}",
+            "mov rbx, {0}",
             inout(reg) request => _,
             inlateout("eax") ENCLU_EGETKEY => error,
             in("rcx") out.as_mut_ptr(),
@@ -64,9 +64,9 @@ pub fn ereport(
 
         asm!(
             // rbx is reserved by LLVM
-            "xchg {}, rbx",
+            "xchg {0}, rbx",
             "enclu",
-            "mov rbx, {}",
+            "mov rbx, {0}",
             inout(reg) targetinfo => _,
             in("eax") ENCLU_EREPORT,
             in("rcx") reportdata,