irqchip: Do not blindly select CONFIG_GENERIC_IRQ_MULTI_HANDLER

Implementing CONFIG_GENERIC_IRQ_MULTI_HANDLER is a decision that is
made at the architecture level, and shouldn't involve the irqchip
at all (we even provide a fallback helper when the option isn't
selected).

Drop all instances of such selection from non-arch code.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210217142800.2547737-1-maz@kernel.org
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Hector Martin <marcan@marcan.st>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>