reboot: x86: prepare reboot_mode for moving to generic kernel code

Prepare for the moving the parsing of reboot= to the generic kernel code
by making reboot_mode into a more generic form.

Change-Id: I6b3ffeaa3dd72a1383c2c04bab81fb8480f1be1b
Signed-off-by: Robin Holt <holt@sgi.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Miguel Boton <mboton.lkml@gmail.com>
Cc: Russ Anderson <rja@sgi.com>
Cc: Robin Holt <holt@sgi.com>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Cc: Guan Xuetao <gxt@mprc.pku.edu.cn>
Acked-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Git-commit: edf2b1394611fef7806d4af72179dc3ac101f275
Git-Repo: git://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/


Signed-off-by: Abhimanyu Kapur <abhimany@codeaurora.org>