platform/x86: dell-wmi-sysman: bound enumeration string aggregation

In the Linux kernel, the following vulnerability has been resolved: platform/x86: dell-wmi-sysman: bound enumeration string aggregation populate_enum_data() aggregates firmware-provided value-modifier and possible-value strings into fixed 512-byte struct members. The current code bounds each individual source string but then appends every string and separator with raw strcat() and no remaining-space check. Switch the aggregation loops to a bounded append helper and reject enumeration packages whose combined strings do not fit in the destination buffers. [ij: add include]