dmaengine: shdma: Move DMA stop to (runtime) suspend callbacks
During system reboot, the sh-dma-engine device may be runtime-suspended,
causing a crash:
Unhandled fault: imprecise external abort (0x1406) at 0x0002c02c
Internal error: : 1406 [#1] SMP ARM
...
PC is at sh_dmae_ctl_stop+0x28/0x64
LR is at sh_dmae_ctl_stop+0x24/0x64
If the sh-dma-engine is runtime-suspended, its module clock is turned
off, and its registers cannot be accessed.
To fix this, move the call to sh_dmae_ctl_stop(), which touches the
DMAOR register, to the sh_dmae_suspend() and sh_dmae_runtime_suspend()
callbacks. This makes PM operations more symmetric, as both
sh_dmae_resume() and sh_dmae_runtime_resume() already call sh_dmae_rst()
to re-initialize the DMAOR register.