file_contexts: Label /dev/ttyS2 as console_device

This fixes the issue with the emulator "-shell" option.
Init tries to open the console which is passed through
the kernel androidboot.console property, but fails to
open it because "avc" denies it. Init only has permissions
to open console_device in rw mode. This ensures that
/dev/ttyS2 is properly labeled as console_device.

Replaced tabs with spaces.

Change-Id: I9ef94576799bb724fc22f6be54f12de10ed56768