kdb: Replace deprecated strcpy() with memcpy() in parse_grep()

kdb: Replace deprecated strcpy() with memcpy() in parse_grep()

strcpy() is deprecated; use memcpy() instead.

We can safely use memcpy() because we already know the length of the
source string 'cp' and that it is guaranteed to be NUL-terminated within
the first KDB_GREP_STRLEN bytes.

Link: https://github.com/KSPP/linux/issues/88
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Signed-off-by: Daniel Thompson (RISCstar) <danielt@kernel.org>