wcnss: Add support to configure the Wlan MAC addr

This change introduces a sysfs entry to allow userspace to
configure the wlan MAC addr and exports an API which allows
WLAN and other wireless technologies to query the wlan MAC
addr

Change-Id: If723ceed9e6cf68533eaa42cef6fab59bb3ae9da
CRs-Fixed: 583465
Signed-off-by: Hardik Kantilal Patel <hkpatel@codeaurora.org>