staging: wlan-ng: rename DIDmsg_p2req_ramdl_write_len in p80211metadef.h

Rename DIDmsg_p2req_ramdl_write_len to DIDMSG_P2REQ_RAMDL_WRITE_LEN to
fix "Avoid CamelCase" message from checkpatch and conform to the
coding style guidelines.

Signed-off-by: Tim Collier <osdevtc@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>