firmware: qcom: scm: Cleanup global '__scm' on probe failures

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: firmware: qcom: scm: Cleanup global '__scm' on probe failures If SCM driver fails the probe, it should not leave global '__scm' variable assigned, because external users of this driver will assume the probe finished successfully. For example TZMEM parts ('__scm->mempool') are initialized later in the probe, but users of it (__scm_smc_call()) rely on the '__scm' variable. This fixes theoretical NULL pointer exception, triggered via introducing probe deferral in SCM driver with call trace: qcom_tzmem_alloc+0x70/0x1ac (P) qcom_tzmem_alloc+0x64/0x1ac (L) qcom_scm_assign_mem+0x78/0x194 qcom_rmtfs_mem_probe+0x2d4/0x38c platform_probe+0x68/0xc8

References

• https://git.kernel.org/stable/c/390d3baeba51a126f75c97b90ec28b9384ce4b84
• https://git.kernel.org/stable/c/faf1715798fe72b79e4432ce8c6d03ca69765425
• https://git.kernel.org/stable/c/1e76b546e6fca7eb568161f408133904ca6bcf4f