hostapd: fix VHT80 for encrypted mesh channel settings

The max_oper_chwidth settings was parsed incorrectly for big endian system.
This prevented the system to switch to VHT80 (or VHT160). Instead they were
mapped to:

* HT20:   20MHz
* VHT20:  20MHz
* HT40:   40MHz
* VHT40:  40MHz
* VHT80:  40MHz
* VHT160: 40MHz

This happened because each max_oper_chwidth setting in the config file was
parsed as "0" instead of the actual value.

Fixes: a4322eba2b12 ("hostapd: fix encrypted mesh channel settings")
Signed-off-by: Sven Eckelmann <sven.eckelmann@openmesh.com>