media: tuners: mxl5005s: remove useless variable assignments

Values assigned to variables Fmax and Fmin at lines 2740 and 2741 are
overwritten at lines 2754 and 2755 before they can be used. This makes
such variable assignments useless.

Addresses-Coverity-ID: 1226952
Addresses-Coverity-ID: 1226953

Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>