clocksource/drivers/oxnas-rps: Fix irq_of_parse_and_map() return value

The irq_of_parse_and_map() returns 0 on failure, not a negative ERRNO.

Fixes: 89355274 ("clocksource/drivers/oxnas-rps: Add Oxford Semiconductor RPS Dual Timer")
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://lore.kernel.org/r/20220422104101.55754-1-krzysztof.kozlowski@linaro.org


Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>