dmaengine: at_hdmac: Remove unnecessary 0x prefixes before %pad

Since commit 3cab1e71 ("lib/vsprintf: refactor duplicate code
to special_hex_number()") %pad doesn't need 0x prefix so drop that.

Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>