mfd: tps65910: Fix possible invalid pointer dereference on regmap_add_irq_chip fail

Fixes: 4aab3fad ("mfd: tps65910: Move interrupt implementation code to mfd file")

tps65910_irq_init() sets 'tps65910->chip_irq' before calling
regmap_add_irq_chip(). If the regmap_add_irq_chip() call fails in
memory allocation of regmap_irq_chip_data members then:

1. The 'tps65910->chip_irq' will still hold some value
2. 'tps65910->irq_data' will be pointing to already freed memory
   (because regmap_add_irq_chip() will free it on error)

This results in invalid memory access during driver remove because the
tps65910_irq_exit() tests whether 'tps65910->chip_irq' is not zero.

Cc: <stable@vger.kernel.org>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>