ARM: shmobile: ape6evm: MP clock parent become EXTAL2

The orignal commit 3263e09d287fbaa8a9424b5e69396599a3bbd518
(ARM: shmobile: Initial r8a73a4 SoC support V3)
put MP clock parent as EXTAL2, but its code was removed
on DIV6 clock support commit.
This patch makes it consistent.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>