x86: Remove unused variable "polling"

Compile tested. "polling" is unused since commit f80c5b39
("sched/idle, x86: Switch from TS_POLLING to TIF_POLLING_NRFLAG").

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Jiri Kosina <jkosina@suse.cz>
Link: http://lkml.kernel.org/r/1404138749.2978.6.camel@x41


Signed-off-by: Ingo Molnar <mingo@kernel.org>