Iron out all extra compiler warnings

Iron out all extra compiler warnings

mbim-msg.c:83:17: error: comparison between signed and unsigned integer expressions
cli.c:50:10: error: comparison between signed and unsigned integer expressions
cli.c:81:10: error: comparison between signed and unsigned integer expressions
cli.c:104:10: error: comparison between signed and unsigned integer expressions
cli.c:140:10: error: comparison between signed and unsigned integer expressions
cli.c:154:18: error: comparison between signed and unsigned integer expressions
cli.c:171:10: error: comparison between signed and unsigned integer expressions
cli.c:194:10: error: comparison between signed and unsigned integer expressions
cli.c:223:10: error: comparison between signed and unsigned integer expressions
cli.c:229:17: error: comparison between signed and unsigned integer expressions
cli.c:241:17: error: comparison between signed and unsigned integer expressions
cli.c:247:17: error: comparison between signed and unsigned integer expressions
cli.c:259:17: error: comparison between signed and unsigned integer expressions
cli.c:272:10: error: comparison between signed and unsigned integer expressions
cli.c:549:16: error: comparison between signed and unsigned integer expressions
mbim-dev.c:68:21: error: comparison between signed and unsigned integer expressions
mbim-dev.c:97:10: error: comparison between signed and unsigned integer expressions

Reviewed-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: Petr Štetiar <ynezz@true.cz>