acpigen: Add helper functions for strings

Add helper function to emit a string into the SSDT AML bytestream with a
NULL terminator.  Also add a helper function to emit the string OpCode
followed by the string itself.

acpigen_emit_string(string)  /* Raw string output */
acpigen_write_string(string) /* OpCode followed by raw string */

Change-Id: I4a3a8728066e0c41d7ad6429fad983e6ae6962fe
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: https://review.coreboot.org/14793
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins)
2 files changed