regulator: tps6594-regulator: Fix random kernel crash

Random kernel crash detected in TI CICD when regulator driver is added.
This is root caused to irq index increment being done twice causing
irq_data being allocated outside of the range.

- Rework tps6594_request_reg_irqs with correct index increment
- Adjust irq_data kmalloc size to the exact size needed for the device

This has been reported on TI mainline. No public bug report associated.

Reported-by: Udit Kumar <u-kumar1@ti.com>
Fixes: f17ccc5d ("regulator: tps6594-regulator: Add driver for TI TPS6594 regulators")
Signed-off-by: Jerome Neanne <jneanne@baylibre.com>
Link: https://lore.kernel.org/r/20230828-tps6594_random_boot_crash_fix-v1-1-f29cbf9ddb37@baylibre.com


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