media: dvb-frontends/dvb-pll: fix module ref-counting

dvb-pll module was 'put' twice on exit:
once by dvb_frontend_detach() and another by dvb_module_release().

Signed-off-by: Akihiro Tsukada <tskd08@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>