qed: replace uses of strncpy

strncpy() is deprecated for use on NUL-terminated destination strings
[1] and as such we should prefer more robust and less ambiguous string
interfaces.

This patch eliminates three uses of strncpy():

Firstly, `dest` is expected to be NUL-terminated which is evident by the
manual setting of a NUL-byte at size - 1. For this use specifically,
strscpy() is a viable replacement due to the fact that it guarantees
NUL-termination on the destination buffer.

The next two cases should simply be memcpy() as the size of the src
string is always 3 and the destination string just wants the first 3
bytes changed.

To be clear, there are no buffer overread bugs in the current code as
the sizes and offsets are carefully managed such that buffers are
NUL-terminated. However, with these changes, the code is now more robust
and less ambiguous (and hopefully easier to read).

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
Link: https://github.com/KSPP/linux/issues/90


Signed-off-by: Justin Stitt <justinstitt@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20231012-strncpy-drivers-net-ethernet-qlogic-qed-qed_debug-c-v2-1-16d2c0162b80@google.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>