ARM: shmobile: r8a73a4: Use shmobile_init_delay()

Adjust the r8a73a4 SoC support code to use shmobile_init_delay()
together with CPU Frequency settings from the DTS. Get rid of the
C code version and r8a73a4_init_early() that now are unused.

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