UBUNTU: SAUCE: x86/entry: Fix up retpoline assembler labels

UBUNTU: SAUCE: x86/entry: Fix up retpoline assembler labels

The extant assembler labels in entry_SYSCALL_64_fastpath
result in the error path incorrectly entering the retpoline logic.
This results in that logic jumping to whatever address is in %r10,
which is the fourth system call argument.

This enables a trivial means to instruct the kernel to jump
to any arbitrary address.  Non-malicious executables making invalid
system calls may also cause the system to crash.

Resolve this by renumbering the assembler labels as is found
in other kernels.

CVE-2017-5753
CVE-2017-5715

Fixes: d2e0236 ("x86/entry: Use retpoline for syscall's indirect calls")
Signed-off-by: Jay Vosburgh <jay.vosburgh@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>