xtensa: clean up Kconfig dependencies for custom cores

	def_bool y

config MMU

	bool

	default n if !XTENSA_VARIANT_CUSTOM

	default XTENSA_VARIANT_MMU if XTENSA_VARIANT_CUSTOM

	def_bool n

config VARIANT_IRQ_SWITCH

	def_bool n

config HAVE_XTENSA_GPIO32

	def_bool n

config MAY_HAVE_SMP

	def_bool n

menu "Processor type and features"

choice

config XTENSA_VARIANT_CUSTOM

	bool "Custom Xtensa processor configuration"

	select MAY_HAVE_SMP

	select HAVE_XTENSA_GPIO32

	help

	  Select this variant to use a custom Xtensa processor configuration.

	bool "Core variant has a Full MMU (TLB, Pages, Protection, etc)"

	depends on XTENSA_VARIANT_CUSTOM

	default y

	select MMU

	help

	  Build a Conventional Kernel with full MMU support,

	  ie: it supports a TLB with auto-loading, page protection.

config HAVE_SMP

	bool "System Supports SMP (MX)"

	depends on MAY_HAVE_SMP

	depends on XTENSA_VARIANT_CUSTOM

	select XTENSA_MX

	help

	  This option is use to indicate that the system-on-a-chip (SOC)