irqchip/mips: Drop selection of IRQ_DOMAIN_HIERARCHY

Now that GENERIC_IRQ_IPI selects IRQ_DOMAIN_HIERARCHY, there is no
need to have this conditional select for IRQ_MIPS_CPU. Similarily,
MIPS_GIC only needs selecting GENERIC_IRQ_IPI.
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Marc Zyngier <maz@kernel.org>

drivers/irqchip/Kconfig

@@ -180,7 +180,6 @@ config IRQ_MIPS_CPU
 	select GENERIC_IRQ_CHIP
 	select GENERIC_IRQ_IPI if SYS_SUPPORTS_MULTITHREADING
 	select IRQ_DOMAIN
-	select IRQ_DOMAIN_HIERARCHY if GENERIC_IRQ_IPI
 	select GENERIC_IRQ_EFFECTIVE_AFF_MASK
 
 config CLPS711X_IRQCHIP
@@ -307,7 +306,6 @@ config KEYSTONE_IRQ
 config MIPS_GIC
 	bool
 	select GENERIC_IRQ_IPI
-	select IRQ_DOMAIN_HIERARCHY
 	select MIPS_CM
 
 config INGENIC_IRQ