[media] af9033: prevent unintended underflow
[media] af9033: prevent unintended underflow

As spotted by Dan Carpenter <ff341aa343d564f9e53e9dcb6996be8c04859a66@oracle.com> (thanks!), we have
improperly used an unsigned variable in a calculation that may result in a
negative number. This may cause an unintended underflow if the interface
frequency of the tuner is > approx. 40MHz.
This patch should resolve the issue, following an approach similar to what is
used in af9013.c.

[293134fe763ce2d9d8609280ea107c73cbd2eb86@iki.fi: add Reported-by]
Reported-by: Dan Carpenter <ff341aa343d564f9e53e9dcb6996be8c04859a66@oracle.com>
Signed-off-by: Hans-Frieder Vogt <0148d981a1a5c25b2bde9a320b939712c8218a94@gmx.net>
Reviewed-by: Antti Palosaari <293134fe763ce2d9d8609280ea107c73cbd2eb86@iki.fi>
Signed-off-by: Antti Palosaari <293134fe763ce2d9d8609280ea107c73cbd2eb86@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <ad86ba2154032c9f55743a190faa2459a9d61d42@redhat.com>

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