TTY: snyclinkmp: forever loop in tx_load_dma_buffer()

My main concern here was the line that said:
	copy_count = min_t(unsigned short,count,SCABUFSIZE);
"count" is an unsigned int here so the cast to unsigned short
truncates the upper bits.  So if count is 0x10000 then copy_count is
0 and the loop never exits.

"count" comes from skb->len in hdlcdev_xmit().

The other min_t() changes are just cleanups.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>