dmaengine/ste_dma40: use AMBA PrimeCell helper macros

The DMA40 is not a PrimeCell from ARM, but it still use the same
ID registers. So let's utilize the existing macros in the
PrimeCell header to identify manufacturer and revision of the IP
block instead of reinventing the wheel.

Cc: Robert Marklund <robert.marklund@stericsson.com>
Cc: Per Forlin <per.forlin@linaro.org>
Cc: Rabin Vincent <rabin.vincent@stericsson.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>