[media] dvb_frontend: fix ioctls failing if frontend open/closed too fast
[media] dvb_frontend: fix ioctls failing if frontend open/closed too fast

That likely fixes this MythTV ticket:
	http://code.mythtv.org/trac/ticket/10830
(which btw affects all usb tuners I tested as well, pctv452e,
dib0700, af9015)  pctv452e is still possibly broken with MythTV
even after this fix; it does work with VDR here tho despite I2C
errors.
Reduced testcase:
	http://people.freebsd.org/~nox/tmp/ioctltst.c
Thanx to devinheitmueller and crope from #linuxtv for helping with
this fix! :)

Signed-off-by: Juergen Lock <db34091a300796f6061e3246e3b203b12c668079@jelal.kn-bremen.de>
Signed-off-by: Michael Krufky <00524723a60798c74a43fcc620c25dd7b9ece078@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <ad86ba2154032c9f55743a190faa2459a9d61d42@redhat.com>

KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs