Although irq_create_mapping() is able to deal with duplicate
mappings, it really isn't supposed to be a substitute for
irq_find_mapping(), and can result in allocations that take place
in atomic context if the mapping didn't exist.

Fix the handful of MFD drivers that use irq_create_mapping() in
interrupt context by using irq_find_mapping() instead.

Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Lee Jones <lee.jones@linaro.org>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Alexandre Torgue <alexandre.torgue@foss.st.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>