wpa_supplicant: Fix parsing of max_oper_chwidth

wpa_supplicant: Fix parsing of max_oper_chwidth

The max_oper_chwidth is parsed in wpa_config_set as INT_RANGE (see
ssid_fields). The actual parsing for INT_RANGE is done by
wpa_config_parse_int which can only store the result as full integer.

max_oper_chwidth is stored as u8 (a single byte) in wpa_ssid. This means
that on little endian systems, the least significant byte of the parsed
value are really stored in the max_oper_chwidth. But on big endian
system, the only most significant byte is stored as max_oper_chwidth.
This means that 0 is always stored because the provided range doesn't
allow any other value for systems with multi-byte-wide integers.

This also means that for common systems with 4-byte-wide integers, the
remaining 3 bytes were written after the actual member of the struct.
This should not have influenced the behavior of succeeding members
because these bytes would have been part of the padding between the
members on most systems.

Increasing its size to a full int fixes the write operations outside of
the member and allows to use the max_oper_chwidth setting on big endian
systems.

Fixes: 0f29bc68d18e ("IBSS/mesh: Add support for VHT80P80 configuration")
Signed-off-by: Sven Eckelmann <sven.eckelmann@openmesh.com>