ARM: shmobile: r8a7779: Wait for status on selected MSTP clocks

When enabling some of the module clocks by clearing stop bits in the
MSTP control registers, the CPG requires waiting for the status
registers to signal that the clocks have started. Failure to do so will
result in returning from the clk_enable() call with the clock
potentially still disabled, leading to various race conditions and
difficult to debug errors.

Enable status wait for all the r8a7779 MSTP clocks that report their
status.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>