ARM: shmobile: Use __init for APMU suspend init function

The function shmobile_smp_apmu_suspend_init() should
be put into the init section to not trigger section
mismatch warnings.

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