Ok -  I put the pieces together:

> iwlwifi 0000:01:00.0: loaded firmware version 22.15.8.0 op_mode iwlmvm
> iwlwifi 0000:01:00.0: Detected Intel(R) Wireless N 7260, REV=0x144

This means that your NIC is 2.4GHz only. Dual band NICs print something
else.

Now here come the catch. You seem to have an "old" NIC in a way that the
NVM (EEPROM like) is old. In that NVM, there was a bug that advertised
the A band channels but disabled the A band in SKU cap.

Can you please try the patch attached?
I will prevent the driver from trying to work on A band while the HW
doesn't allow.

emmanuel