Revert "ARM: shmobile: r8a7779: Replace modify_scu_cpu_psr with scu_power_mode"

This reverts commit cdc7594e.

The code changes the flags of the wrong cpus - which breaks the whole
bootup of secondary CPUs.

Cc: Bastian Hecht <hechtb@gmail.com>
Signed-off-by: Simon Horman <horms@verge.net.au>