mfd: fsl-imx25: Fix an error handling path in mx25_tsadc_setup_irq()

If devm_of_platform_populate() fails, some resources need to be
released.

Introduce a mx25_tsadc_unset_irq() function that undoes
mx25_tsadc_setup_irq() and call it both from the new error handling path
of the probe and in the remove function.

Fixes: a55196ef ("mfd: fsl-imx25: Use devm_of_platform_populate()")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/d404e04828fc06bcfddf81f9f3e9b4babbe35415.1659269156.git.christophe.jaillet@wanadoo.fr