reboot: arm: change reboot_mode to use enum reboot_mode

Preparing to move the parsing of reboot= to generic kernel code forces
the change in reboot_mode handling to use the enum.

Change-Id: I4ef2b002074e1205ee141539bfe60d06735ce5f4
[akpm@linux-foundation.org: fix arch/arm/mach-socfpga/socfpga.c]
Signed-off-by: Robin Holt <holt@sgi.com>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Cc: Russ Anderson <rja@sgi.com>
Cc: Robin Holt <holt@sgi.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Guan Xuetao <gxt@mprc.pku.edu.cn>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Git-commit: 7b6d864b48d95e6ea1df7df64475b9cb9616dcf9
Git-Repo: git://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/


[abhimany@codeaurora.org: make similar changes for mach-msm]
Signed-off-by: Abhimanyu Kapur <abhimany@codeaurora.org>