sunhme: Uninitialized variable in happy_meal_init()

The "burst" string is only initialized for CONFIG_SPARC.  It should be
set to "64" because that's what is used by PCI.

Fixes: 24cddbc3 ("sunhme: Combine continued messages")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Sean Anderson <seanga2@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>