regmap: irq: Free the irqdomain we create

When domain support was added to regmap-irq it was not possible to
remove domains, this was added later by 8ee99ada293b (irqdomain: Support
removal of IRQ domains.).  We did update the main removal path to free
the domain but forgot the error unwinding case during creation that is
now in regmap_add_irq_chip_fwnode() after some code motion, meaning that
errors during instantiation result in an unused irqchip being left
hanging around.  Add the missing irq_remove_domain() call where the
comment says it should be.

Reported-by: Farhad Alemi <farhad.alemi@berkeley.edu>
Reported-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260901-regmap-irq-deallocate-domain-v1-1-4bfed4aff559@kernel.org
Signed-off-by: Mark Brown <broonie@kernel.org>