Fix sysret test for C3 machines.

C3 machines have 5-level page tables enabled, which support 57 bits for virtual
addresses. So update `kNonCanonicalRsp` so it induces the SIGBUS failure for
5-level page table x86 systems too.

Suggested-by: Andrei Vagin <avagin@google.com>
PiperOrigin-RevId: 632581917

test/syscalls/linux/sysret.cc

@@ -29,7 +29,7 @@ namespace testing {
 namespace {
 
 constexpr uint64_t kNonCanonicalRip = 0xCCCC000000000000;
-constexpr uint64_t kNonCanonicalRsp = 0xFFFF000000000000;
+constexpr uint64_t kNonCanonicalRsp = 0xFE00000000000000;
 
 class SysretTest : public ::testing::Test {
  protected: