memory: stm32_omm: Fix req2ack update test

If "st,omm-req2ack-ns" property is found and its value is not 0,
the current test doesn't allow to compute and set req2ack value,
Fix this test.

Fixes: 8181d061 ("memory: Add STM32 Octo Memory Manager driver")
Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>
Link: https://lore.kernel.org/r/20250807-upstream_omm_fix_req2ack_test_condition-v2-1-d7df4af2b48b@foss.st.com


Cc: <stable@vger.kernel.org>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>