V4L/DVB (7630): au8522: fix au8522_read_ucblocks for qam

ucblocks are reported in separate registers for vsb & qam

Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>