soc: samsung: exynos-pmu: Fix uninitialized ret in tensor_set_bits_atomic()

soc: samsung: exynos-pmu: Fix uninitialized ret in tensor_set_bits_atomic()

If tensor_set_bits_atomic() is called with a mask of 0 the function will
just iterate over its bit, not perform any updates and return stack
value of 'ret'.

Also reported by smatch:

  drivers/soc/samsung/exynos-pmu.c:129 tensor_set_bits_atomic() error: uninitialized symbol 'ret'.

Fixes: 0b7c6075022c ("soc: samsung: exynos-pmu: Add regmap support for SoCs that protect PMU regs")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20250104135605.109209-1-krzysztof.kozlowski@linaro.org
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>