char: xillybus: Fix condition for invoking the xillybus/ subdirectory

As Xillybus' configuration symbol hierarchy has been reorganized recently,
the correct condition for compiling the xillybus/ subdirectory is now
CONFIG_XILLYBUS_CLASS, and not CONFIG_XILLYBUS.
Reported-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Eli Billauer <eli.billauer@gmail.com>
Link: https://lore.kernel.org/r/20210528092242.51104-1-eli.billauer@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/char/Makefile

@@ -44,6 +44,6 @@ obj-$(CONFIG_TCG_TPM)		+= tpm/
 
 obj-$(CONFIG_PS3_FLASH)		+= ps3flash.o
 
-obj-$(CONFIG_XILLYBUS)		+= xillybus/
+obj-$(CONFIG_XILLYBUS_CLASS)	+= xillybus/
 obj-$(CONFIG_POWERNV_OP_PANEL)	+= powernv-op-panel.o
 obj-$(CONFIG_ADI)		+= adi.o