sysvinit-inittab: fix getty device removal

sysvinit-inittab: fix getty device removal

getty devices were not being removed in some cases because device name
was not at the end of the line, for example a ttyS1 device:

S1:12345:respawn:/bin/start_getty 115200 ttyS1 vt102

Removing this limitation allows sed to remove any line containing
the device.

Signed-off-by: Leonardo Sandoval <leonardo.sandoval.gonzalez@linux.intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>