net: wireless: bcmdhd: add boundary check in dhd_rtt_event_handler

added boundary check for input parameters not to corrupt kernel heap in
case user injected malformed input

Signed-off-by: Insun Song <insun.song@broadcom.com>
Bug: 37305578
Change-Id: I92114d7166fb68d8d97b33ea214f80e8917794d1