drm/msm/dp: fix error check return value of irq_of_parse_and_map()

The irq_of_parse_and_map() function returns 0 on failure, and does not
return an negative value.

Fixes: 8ede2ecc ("drm/msm/dp: Add DP compliance tests on Snapdragon Chipsets")
Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: Lv Ruyi <lv.ruyi@zte.com.cn>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/483176/
Link: https://lore.kernel.org/r/20220424032418.3173632-1-lv.ruyi@zte.com.cn


Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>