staging: unisys: Fix CamelCase in Issue_VMCALL_IO_VISORSERIAL_ADDR()

Fix CamelCase names:
Issue_VMCALL_IO_VISORSERIAL_ADDR => issue_vmcall_io_visorserial_addr
DiagChannelAddress => channel_addr

Signed-off-by: Benjamin Romer <benjamin.romer@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>