port-evbmips/60412: Sysinst shows wrong kernel names for evbmips-mips64

["Andreas Gustafsson via gnats" <gnats-admin%NetBSD.org@localhost>]

>Number:         60412
>Category:       port-evbmips
>Synopsis:       Sysinst shows wrong kernel names for evbmips-mips64
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    port-evbmips-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Jul 05 08:50:00 +0000 2026
>Originator:     Andreas Gustafsson
>Release:        NetBSD 9.2
>Organization:
  
>Environment:
System: NetBSD
Architecture: evbmips
Machine: mips64eb
>Description:

When running sysinst on evbmips-mips64eb, the names of the kernel sets
shown in the set selection menu don't match the actual filenames that
are installed when you select them.  For example, the set selection
menu shows "a: Kernel (ALCHEMY)", but if you select it, sysinst will
actually attempt to install kern-XLSATX64.

This is because different evbmips variants have different kernel set
names selected by conditional compilation in sysinst/arch/evbmips/md.h,
but sysinst/arch/evbmips/msg.md.* only define a single set of display
strings shared by all variants.

>How-To-Repeat:

If you have an erlite3 whose flash drive contents you don't mind
losing, netboot the INSTALL_OCTEON kernel on it and attempt an install
(which is expected to fail for reasons not limited to the present PR).
Choose any kernel set, and then watch sysinst install a different one
that wasn't even among the choices.

>Fix: