ARM: 8121/1: smp_scu: use macro for SCU enable bit

Use macro instead of magic number for SCU enable bit.

Signed-off-by: Shawn Guo <shawn.guo@freescale.com>
Acked-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>