ARM: shmobile: r8a7779: Use rcar_sysc_power_{down,up}_cpu()

The r8a7779 SMP code calls rcar_sysc_power_{down,up}() to control power
to the SYSC power areas containing CPUs. This requires passing full CPU
power area parameter blocks.

Migrate the code to call the new rcar_sysc_power_{down,up}_cpu()
helpers, which just take a CPU index, and use the SYSC power area
definitions from the r8a7779-sysc driver.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>