ARM: shmobile: Add shared shmobile_init_delay()

Introduce shmobile_init_delay() that gets CPU specific
parameters from DT and sets up the early delay from
there. This allows us to both remove frequency information
from the C code and consolidate existing code.

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