libusb calls timerfd_create() and timerfd_settime() when it's built with
timerfd support.

Command to reproduce:

       -device usb-host,hostbus=1,hostaddr=3,id=hostdev0

Log messages:

audit(1390730418.924:135): auid=4294967295 uid=121 gid=103 ses=4294967295
                           pid=5232 comm="qemu-system-x86" sig=31 syscall=283
                           compat=0 ip=0x7f2b0f4e96a7 code=0x0
audit(1390733100.580:142): auid=4294967295 uid=121 gid=103 ses=4294967295
                           pid=16909 comm="qemu-system-x86" sig=31 syscall=286
                           compat=0 ip=0x7f03513a06da code=0x0

Reading a few hundred MB from a USB drive on x86_64 shows this syscall distribution.
Therefore the timerfd_settime priority is set to 242.

    calls  syscall
 --------- ----------------
   5303600 write
   2240554 read
   2167030 ppoll
   2134828 ioctl
    704023 timerfd_settime
    689105 poll
     83122 futex
       803 writev
       476 rt_sigprocmask
       287 recvmsg
       178 brk

Signed-off-by: Felix Geyer <debfx@fobos.de>
Signed-off-by: Eduardo Otubo <otubo@linux.vnet.ibm.com>