platform/mips: Adjust Kconfig to keep consistency

Drop the "if MIPS" and "endif" drivers/platform/Kconfig. Instead add
a "depends on MIPS" to "menuconfig MIPS_PLATFORM_DEVICES" in drivers/
platform/mips/Kconfig, like all the other subdirs are doing.
Suggested-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

drivers/platform/Kconfig

 # SPDX-License-Identifier: GPL-2.0-only
-if MIPS
 source "drivers/platform/mips/Kconfig"
-endif
 
 source "drivers/platform/loongarch/Kconfig"
 

drivers/platform/mips/Kconfig

@@ -6,6 +6,7 @@
 menuconfig MIPS_PLATFORM_DEVICES
 	bool "MIPS Platform Specific Device Drivers"
 	default y
+	depends on MIPS
 	help
 	  Say Y here to get to see options for device drivers of various
 	  MIPS platforms, including vendor-specific netbook/laptop/desktop