CVE-2026-98830: wifi: wfx: validate MIB read length before copying to caller

In the Linux kernel, the following vulnerability has been resolved:

wifi: wfx: validate MIB read length before copying to caller

wfxhifreadmib() copies reply->length bytes from the firmware response into the caller-provided buffer without checking that reply->length does not exceed vallen. A firmware response with a length field larger than expected overruns the caller buffer and reads past the end of the reply allocation.

Replace the dead -ENOMEM check with an active validation that reply->length fits within vallen before the memcpy.