sysvinit-inittab: Add wrapper script to verify console exists

Add a wrapper script around getty to check if a given console exists, this
allows for multiple Console ttys to be specified for various boards without
having additional BSP types just for different console types.

[YOCTO #8689]

Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>