sysvinit-inittab: Add support for tty devices with 10 or more number.

sysvinit-inittab: Add support for tty devices with 10 or more number.

"start_getty" support for tty devices with under 10 number.
When SERIAL_CONSOLES has tty devices with 10 or more number,
do not't start getty and output the following message.
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sh 1: unknown operand
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Signed-off-by: Yuki Hoshino <yuki.hoshino@miraclelinux.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>