wifi: mt76: mt7925: fix country count limitation for CLC

wifi: mt76: mt7925: fix country count limitation for CLC

Due to the increase in the number of power tables for 6Ghz on CLC,
the variable nr_country is no longer sufficient to represent the
total quantity. Therefore, we have switched to calculating the
length of clc buf to obtain the correct power table.

Cc: stable@vger.kernel.org
Fixes: c948b5da6bbe ("wifi: mt76: mt7925: add Mediatek Wi-Fi7 driver for mt7925 chips")
Signed-off-by: Ming Yen Hsieh <mingyen.hsieh@mediatek.com>
Link: https://patch.msgid.link/20250116062131.3860198-1-mingyen.hsieh@mediatek.com
Signed-off-by: Felix Fietkau <nbd@nbd.name>