Input: synaptics-rmi4 - fix F03 build error when serio is module

Since F03 is a boolean, "depends" on symbols that can be modules
do not work quite right. We can enable F03 if SERIO is built-in or
if both RMI core and SERIO core are modules. If SERIO core is module,
but RMI is built-in, we'll get:

drivers/built-in.o: In function `rmi_f03_attention':
rmi_f03.c:(.text+0xf8ef8): undefined reference to `serio_interrupt'
rmi_f03.c:(.text+0xf8fbd): undefined reference to `serio_interrupt'
drivers/built-in.o: In function `rmi_f03_remove':
rmi_f03.c:(.text+0xf9082): undefined reference to `serio_unregister_port'
drivers/built-in.o: In function `rmi_f03_probe':
rmi_f03.c:(.text+0xf9260): undefined reference to `__serio_register_port'

Reported-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/rmi4/Kconfig

@@ -41,7 +41,8 @@ config RMI4_SMB
 
 config RMI4_F03
         bool "RMI4 Function 03 (PS2 Guest)"
-        depends on RMI4_CORE && SERIO
+	depends on RMI4_CORE
+	depends on SERIO=y || RMI4_CORE=SERIO
         help
           Say Y here if you want to add support for RMI4 function 03.