spi: fsl: use platform_get_irq() instead of of_irq_to_resource()

Unlike irq_of_parse_and_map() which has a dummy definition on SPARC,
of_irq_to_resource() hasn't.

But as platform_get_irq() can be used instead and is generic, use it.

Reported-by: kbuild test robot <lkp@intel.com>
Suggested-by: Mark Brown <broonie@kernel.org>
Fixes: 	3194d253 ("spi: fsl: don't map irq during probe")
Cc: stable@vger.kernel.org
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Link: https://lore.kernel.org/r/091a277fd0b3356dca1e29858c1c96983fc9cb25.1576172743.git.christophe.leroy@c-s.fr


Signed-off-by: Mark Brown <broonie@kernel.org>