By cleaning up the code the compiler does not emit the following warning
anymore:

    src/base64.c:15:19: warning: duplicate ‘const’ declaration specifier [-Wduplicate-decl-specifier]
     static const char const uuenc_tbl_base64[65 + 1] = {
                       ^~~~~

Signed-off-by: Ulrich Ölmann <u.oelmann@pengutronix.de>
Signed-off-by: Roland Hieber <rhi@pengutronix.de>