gsmi: Add coreboot to list of matching BIOS vendors

In order to use this coreboot needs board support for:
CONFIG_ELOG=y
CONFIG_ELOG_GSMI=y

And the kernel driver needs enabled:
CONFIG_GOOGLE_GSMI=y

To test, verify that clean shutdown event is added to the log:

> mosys eventlog list | grep 'Clean Shutdown'
11 | 2012-06-25 09:49:24 | Kernl Event | Clean Shutdown

Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-by: Stefan Reinauer <reinauer@chromium.org>
Signed-off-by: Furquan Shaikh <furquan@google.com>
Tested-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Justin TerAvest <teravest@chromium.org>
[zwisler: update changelog for upstream]
Signed-off-by: Ross Zwisler <zwisler@google.com>
Reviewed-by: Guenter Roeck <groeck@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>