ARM: shmobile: r8a7791: Wait for status on all MSTP clocks

ARM: shmobile: r8a7791: Wait for status on all MSTP clocks

When enabling a module clock by clearing its bit in the MSTP control
register, the CPG requires waiting for the status register to signal
that the clock has 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 MSTP clocks on the r8a7791.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
(cherry picked from commit dd6fc76d2f61e732a14f3592bdd83c2c0b7d2dcc)
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>