ARM: S3C24XX: fix redundant checks in the irq mapping function

ARM: S3C24XX: fix redundant checks in the irq mapping function

The check during the parent handling itself was wrong, as it should have
checked for parent_irq_data.

The interrupt controller structs always contain an irq_data array with 32
entries and the only possible error could be a parent_irq assignment of >31.

As this would point to outside the irq_data array this could contain
anything including non-NULL values. Therefore correct this to check
the parent_irq value to be in the right range.

With the same explanation of a valid interrupt controller always having a
full irq_data array, the topmost irq_data check in s3c24xx_irq_map
can also go away.

Finally the mapping function is only called thru the irq_domain ops, in
which case the intc struct is already successfully created, so there is
no need to check for it again.

Reported-by: Julia Lawall <julia.lawall@lip6.fr>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>