kconfig: lxdialog: replace strcpy with snprintf in print_autowrap

strcpy() does not perform bounds checking and can lead to buffer overflows
if the source string exceeds the destination buffer size. In
print_autowrap(), replace strcpy() with snprintf() to safely copy the
prompt string into the fixed-size tempstr buffer.

Signed-off-by: Suchit Karunakaran <suchitkarunakaran@gmail.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>