dmaengine: PL08x: remove runtime PM support

The runtime PM support conflicts with the generic AMBA bus PM, and also
causes a potential deadlock with the PL011 driver as it results in
interrupts being enabled beneath a spinlock.

I don't presently see any solution to this other than by removing the
runtime PM support entirely from the DMA engine driver.  Alternative
suggestions welcome.

Acked-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>