x86: Nuke GET_THREAD_INFO_WITH_ESP() macro for i386

According to a git log -p, GET_THREAD_INFO_WITH_ESP() has only been defined
and never been used. Get rid of it.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20140206144321.409045251@goodmis.org
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>