PCI: endpoint: epf-mhi: Avoid NULL dereference if DT lacks 'mmio'

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: PCI: endpoint: epf-mhi: Avoid NULL dereference if DT lacks 'mmio' If platform_get_resource_byname() fails and returns NULL because DT lacks an 'mmio' property for the MHI endpoint, dereferencing res->start will cause a NULL pointer access. Add a check to prevent it. [kwilczynski: error message update per the review feedback] [bhelgaas: commit log]

References

• https://git.kernel.org/stable/c/242ee2b0ad9b23f47084904fce3f9f228068a1f9
• https://git.kernel.org/stable/c/c8b9d6b7d62a444e0bca5b9ae28f9f2b0f52feef
• https://git.kernel.org/stable/c/0e6d92e3b973de78eb7015154cf1197af9fac5c9
• https://git.kernel.org/stable/c/5089b3d874e9933d9842e90410d3af1520494757