x86,nospec: Simplify {JMP,CALL}_NOSPEC

x86,nospec: Simplify {JMP,CALL}_NOSPEC

commit 09d09531a51a24635bc3331f56d92ee7092f5516 upstream.

Have {JMP,CALL}_NOSPEC generate the same code GCC does for indirect
calls and rely on the objtool retpoline patching infrastructure.

There's no reason these should be alternatives while the vast bulk of
compiler generated retpolines are not.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>