[media] media: tuner xc5000 - release firmwware from xc5000_release()

xc5000 releases firmware right after loading it. Change it to
save the firmware and release it from xc5000_release(). This
helps avoid fecthing firmware when forced firmware load requests
come in to change analog tv frequence and when firmware needs to
be reloaded after suspend and resume.

Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>