Staging: bcm: Add size maximum size restrictions for IOCTL_IDLE_REQ

In the first alteration, the MAX_CNTL_PKT_SIZE is the
maximum size of the control packet in ->Adapter->txctlpacket[]
which is defined in InitAdapter(). This caps the size of
kmalloc memory allocation. In the second change, this max
cap fixes a potential memory corruption bug when subsequent
memset and memcpy calls are invoked.

Signed-off-by: Kevin McKinney <klmckinney1@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>