crypto: hisilicon/qm - set NULL to qm->debug.qm_diff_regs

In the Linux kernel, the following vulnerability has been resolved: crypto: hisilicon/qm - set NULL to qm->debug.qm_diff_regs When the initialization of qm->debug.acc_diff_reg fails, the probe process does not exit. However, after qm->debug.qm_diff_regs is freed, it is not set to NULL. This can lead to a double free when the remove process attempts to free it again. Therefore, qm->debug.qm_diff_regs should be set to NULL after it is freed.