drm: zynqmp_dp: Fix a deadlock in zynqmp_dp_ignore_hpd_set()

In the Linux kernel, the following vulnerability has been resolved: drm: zynqmp_dp: Fix a deadlock in zynqmp_dp_ignore_hpd_set() Instead of attempting the same mutex twice, lock and unlock it. This bug has been detected by the Clang thread-safety analyzer.