Staging: wlan-ng: Drop wrapper function

Drop the function prism2mgmt_pstr2bytearea and replace its function call
with the standard function memcpy that it wrapped.
The code becomes cleaner after this patch.

Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>