regulator: pf0900: Make regu_irqs variable static const

regulator: pf0900: Make regu_irqs variable static const

File-scope 'regu_irqs' is not used outside of this unit and is not
modified anywhere, so make it static const to silence sparse warning:

  pf0900-regulator.c:774:29: warning: symbol 'regu_irqs' was not declared. Should it be static?

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Link: https://patch.msgid.link/20260216085804.69102-2-krzysztof.kozlowski@oss.qualcomm.com
Signed-off-by: Mark Brown <broonie@kernel.org>