Fix incorrect hardware address on systems without getifaddrs()

Fix incorrect hardware address on systems without getifaddrs()

On unix systems for which QT_NO_GETIFADDRS is defined, the way that the
hardware address field is extracted from the result of a call to
qt_safe_ioctl() is incorrect. The address of the ifreq.ifr_addr struct
is taken rather than the appropriate member within that struct, sa_data,
resulting in a memory offset and subsequently the hardware address has
garbage in the first two of six fields. This commit modifies the code
to pass the sa_data member instead of the address of the struct as a
whole.

Task-number: QTBUG-19165
Merge-request: 2614
Reviewed-by: Martin Petersson
(cherry picked from commit 004ad12669ef696eeba70fd57d1eb0c67c806d1d)