net: 6pack: Fix tx timeout and slot time

tx timeout and slot time are currently specified in units of HZ.  On
Alpha, HZ is defined as 1024.  When building alpha:allmodconfig, this
results in the following error message.

  drivers/net/hamradio/6pack.c: In function 'sixpack_open':
  drivers/net/hamradio/6pack.c:71:41: error:
  	unsigned conversion from 'int' to 'unsigned char'
  	changes value from '256' to '0'

In the 6PACK protocol, tx timeout is specified in units of 10 ms and
transmitted over the wire:

    https://www.linux-ax25.org/wiki/6PACK

Defining a value dependent on HZ doesn't really make sense, and
presumably comes from the (very historical) situation where HZ was
originally 100.

Note that the SIXP_SLOTTIME use explicitly is about 10ms granularity:

        mod_timer(&sp->tx_t, jiffies + ((when + 1) * HZ) / 100);

and the SIXP_TXDELAY walue is sent as a byte over the wire.
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/net/hamradio/6pack.c

@@ -68,9 +68,9 @@
 #define SIXP_DAMA_OFF		0
 
 /* default level 2 parameters */
-#define SIXP_TXDELAY			(HZ/4)	/* in 1 s */
+#define SIXP_TXDELAY			25	/* 250 ms */
 #define SIXP_PERSIST			50	/* in 256ths */
-#define SIXP_SLOTTIME			(HZ/10)	/* in 1 s */
+#define SIXP_SLOTTIME			10	/* 100 ms */
 #define SIXP_INIT_RESYNC_TIMEOUT	(3*HZ/2) /* in 1 s */
 #define SIXP_RESYNC_TIMEOUT		5*HZ	/* in 1 s */