Staging:unisys: Add Kconfig dependency on UNISYS_VISORUTIL to UNISYS_CHANNELSTUB

The visorchannelstub module references the variable unisys_spar_platform
which is declared in the visorutil module.  Add the proper dependency to
Kconfig to ensure that visorutil is enabled when building visorchannelstub.

This address the build error:
   drivers/built-in.o: In function `channel_mod_init':
   chanstub.c:(.init.text+0xbe24): undefined reference to `unisys_spar_platform'

Reported by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Ken Cox <jkc@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/unisys/channels/Kconfig

@@ -4,7 +4,7 @@
 
 config UNISYS_CHANNELSTUB
 	tristate "Unisys channelstub driver"
-	depends on UNISYSSPAR
+	depends on UNISYSSPAR && UNISYS_VISORUTIL
 	---help---
 	If you say Y here, you will enable the Unisys channels driver.