ARM: shmobile: Remove shmobile_setup_delay()

All ARM mach-shmobile SoCs and boards now rely on DTS for
CPU Frequency information, so remove the unused function
shmobile_setup_delay(). While at it, make the function
shmobile_setup_delay_hz() static.

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