libbb: use <poll.h> instead of <sys/poll.h>

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

runit/sv.c

@@ -169,7 +169,6 @@ Exit Codes
 //usage:       "pause, cont, hup, alarm, interrupt, quit, 1, 2, term, kill: send\n"
 //usage:       "STOP, CONT, HUP, ALRM, INT, QUIT, USR1, USR2, TERM, KILL signal to service"
 
-#include <sys/poll.h>
 #include <sys/file.h>
 #include "libbb.h"
 #include "runit_lib.h"