pstore/ram: Add ramoops_console_write_buf api

Allow writing into the ramoops console buffer.

Change-Id: Iff0d69b562e4dae33ea7f8d19412227bebb17e47
Signed-off-by: Arve Hjønnevåg <arve@android.com>
Git-commit: 3e966cff406d9b43a16e07291a918cb2a098e32f
Git-repo: https://android.googlesource.com/kernel/common.git


Signed-off-by: Ian Maund <imaund@codeaurora.org>