mfd: max77620: Do not allocate IRQs upfront

regmap_add_irq_chip() will try to allocate all of the IRQ descriptors
upfront if passed a non-zero irq_base parameter. However, the intention
is to allocate IRQ descriptors on an as-needed basis if possible. Pass 0
instead of -1 to fix that use-case.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

include/linux/mfd/max77620.h

@@ -329,7 +329,6 @@ struct max77620_chip {
 	struct regmap *rmap;
 
 	int chip_irq;
-	int irq_base;
 
 	/* chip id */
 	enum max77620_chip_id chip_id;