irqdomain: Refactor __irq_domain_alloc_irqs()

irqdomain: Refactor __irq_domain_alloc_irqs()

commit f45473c201a0974d31ae27651cb0d653e183a1b9 upstream.

Refactor __irq_domain_alloc_irqs() so that it can be called internally
while holding the irq_domain_mutex.

This will be used to fix a shared-interrupt mapping race, hence the
Fixes tag.

Fixes: d6f9a7c319af ("irqdomain: Fix handling of type settings for existing mappings")
Cc: stable@vger.kernel.org      # 4.8
Tested-by: Hsin-Yi Wang <hsinyi@chromium.org>
Tested-by: Mark-PK Tsai <mark-pk.tsai@mediatek.com>
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20230213104302.17307-6-johan+linaro@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>