V4L/DVB (13589): dib8000: merge two conditionals

Merge two ifs: the condition is the same. The second if
uses the ncoeff which is initialized in the first if.

Cc: Patrick Boettcher <pboettcher@kernellabs.com>
Signed-off-by: Márton Németh <nm127@freemail.hu>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>