Three small x86 fixes which did not make it into 6.1:
- Remove a superfluous noinline which prevents GCC-7.3 to optimize a stub
function away.
- Allow uprobes on REP NOP and do not treat them like word-sized branch
instructions.
- Make the VDSO symbol export of __vdso_sgx_enter_enclave() depend on
CONFIG_X86_SGX to prevent build fails with newer LLVM versions which
rightfully detect that there is no function behind the symbol.