MFC r339931,r339933:

MFC r339931,r339933:

   As a follow-up to r339930 (r339951 in stable/12) and various reports
   implement logging in case we fail during module load because the pcpu
   or vnet module sections are full.
   We did return a proper error but not leaving any indication to the
   user as to what the actual problem was.

   Even worse, on 12/13 currently we are seeing an unrelated error (ENOSYS
   instead of ENOSPC, which gets skipped over in kern_linker.c) to be
   printed which made problem diagnostics even harder.

PR:		228854

Approved by:	re (kib)