ARM: sa1100: clear reset status prior to reboot

Clear the current reset status prior to rebooting the platform.  This
adds the bit missing from 04fef228 ("[ARM] pxa: introduce
reset_status and clear_reset_status for driver's usage").

Fixes: 04fef228 ("[ARM] pxa: introduce reset_status and clear_reset_status for driver's usage")
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>