UBUNTU-CVE-2026-80993: Medium severity ubuntu/linux-hwe-edge vulnerability

In the Linux kernel, the following vulnerability has been resolved: net: phylink: correctly validate returned PCS in phylinkinbandcaps In phylinkinbandcaps(), the PCS returned by macselectpcs is only checked if NULL but macselectpcs can also return an error pointer. This can cause a kernel panic as phylinkpcsinbandcaps() only checks if passed PCS is not NULL and directly dereference ops from the phylinkpcs struct. Use the ISERRORNULL macro to address both case where the returned PCS can be NULL or an error pointer and prevent a kernel panic.