ARM: shmobile: Use shmobile_init_delay() on r7s72100

Adjust the r7s72100 SoC support code to use shmobile_init_delay()
together with CPU Frequency settings from the DTS. Get rid of the
C code version.

Signed-off-by: Magnus Damm <damm+renesas@opensource.se>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>