reboot: move arch/x86 reboot= handling to generic kernel

reboot: move arch/x86 reboot= handling to generic kernel

Merge together the unicore32, arm, and x86 reboot= command line
parameter handling.

Signed-off-by: Robin Holt <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Russell King <[email protected]>
Cc: Guan Xuetao <[email protected]>
Cc: Russ Anderson <[email protected]>
Cc: Robin Holt <[email protected]>
Acked-by: Ingo Molnar <[email protected]>
Acked-by: Guan Xuetao <[email protected]>
Acked-by: Russell King <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>