sbshc: acpi_device_class "smbus_host_controller" too long

acpi_device_class can only be 19 characters and a NULL terminator.

With the current name we get a buffer overflow in acpi_smbus_hc_add()
when we do:
	strcpy(acpi_device_class(device), ACPI_SMB_HC_CLASS);

Signed-off-by: Dan Carpenter <error27@gmail.com>
Cc: Alexey Starikovskiy <astarikovskiy@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Len Brown <len.brown@intel.com>