ARM: shmobile: Rework EMEV2 scu_base variable

Rename the static scu_base variable into shmobile_scu_base.

Later in the series the shmobile_scu_base variable will be
made into a global variable so this is preparation only.

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>