i2c: keba: I2C_KEBA should depend on KEBA_CP500

The KEBA I2C controller is only present on KEBA PLC devices. Hence add
a dependency on KEBA_CP500, to prevent asking the user about this driver
when configuring a kernel without KEBA CP500 system FPGA support.

Fixes: c7e08c816cd2fdf8 ("i2c: keba: Add KEBA I2C controller support")
Signed-off-by: Geert Uytterhoeven <[e-mail]>
Reviewed-by: Gerhard Engleder <[e-mail]>
Signed-off-by: Andi Shyti <[e-mail]>

drivers/i2c/busses/Kconfig

···
 config I2C_KEBA
 	tristate "KEBA I2C controller support"
 	depends on HAS_IOMEM
+	depends on KEBA_CP500 || COMPILE_TEST
 	select AUXILIARY_BUS
 	help
 	  This driver supports the I2C controller found in KEBA system FPGA