irqdomain: Make __irq_domain_create() return an error code

__irq_domain_create() can fail for several reasons. When it fails it
returns a NULL pointer and so filters out the exact failure reason.
The only user of __irq_domain_create() is irq_domain_instantiate() which
can return a PTR_ERR value. On __irq_domain_create() failure, it uses an
arbitrary error code.

Rather than using this arbitrary error value, make __irq_domain_create()
return is own error code and use that one.

[ tglx: Remove the pointless ERR_CAST. domain is a valid return pointer ]

Signed-off-by: Herve Codina <herve.codina@bootlin.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240614173232.1184015-11-herve.codina@bootlin.com