irqchip/sifive-plic: remove user selectability of SIFIVE_PLIC

The SiFive PLIC driver is used by all current implementations, including
those that do not have a SiFive PLIC. The current driver supports more
than just SiFive PLICs at present and, where possible, future PLIC
implementations will also use this driver. As every supported RISC-V SoC
selects the driver directly in Kconfig.socs there's no point in exposing
this kconfig option to users.

The Kconfig help text, in its current form, is misleading. There's no
point doing anything about that though, as it will no longer be user
selectable. Remove it.

Suggested-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20221118104300.85016-2-conor@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

drivers/irqchip/Kconfig

@@ -551,18 +551,10 @@ config RISCV_INTC
 	   If you don't know what to do here, say Y.
 
 config SIFIVE_PLIC
-	bool "SiFive Platform-Level Interrupt Controller"
+	bool
 	depends on RISCV
 	select IRQ_DOMAIN_HIERARCHY
 	select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
-	help
-	   This enables support for the PLIC chip found in SiFive (and
-	   potentially other) RISC-V systems.  The PLIC controls devices
-	   interrupts and connects them to each core's local interrupt
-	   controller.  Aside from timer and software interrupts, all other
-	   interrupt sources are subordinate to the PLIC.
-
-	   If you don't know what to do here, say Y.
 
 config EXYNOS_IRQ_COMBINER
 	bool "Samsung Exynos IRQ combiner support" if COMPILE_TEST