iommu/arm-smmu: Remove duplicate error message

Since commit 7723f4c5 ("driver core: platform: Add an error message
to platform_get_irq*()"), platform_get_irq() displays an error when the
IRQ isn't found. Remove the error print from the SMMU driver. Note the
slight change of behaviour: no message is printed if platform_get_irq()
returns -EPROBE_DEFER, which probably doesn't concern the SMMU.

Fixes: 7723f4c5 ("driver core: platform: Add an error message to platform_get_irq*()")
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Joerg Roedel <jroedel@suse.de>