wlan: Static source code analysis fixes for HDD

Fix a potential buffer overflow bug which may happen when we try to write
the zero terminator to the end of an array.

Also we should use copy_from_user() to perform deep copies of the data that
wrqu->data.pointer references from IOCTL interface.

Change-Id: I9e5bfe6acde10b43f810981c57aa526b1ed0333a
CRs-fixed: 554890, 561023