Fix IIC "how" argument dereferencing on big-endian platforms

"how" argument is passed as value of int* pointer to callback
function but dereferenced as char* so only one byte taken into
into account. On little-endian systems it happens to work because
first byte is LSB that contains actual value, on big-endian it's
MSB and in this case it's always equal zero

PR: 207786
Submitted by: chadf@triularity.org