spi: atmel: fix printk format warnings

Fix printk format warning by using %p extension 'ad' for dma_addr_t.

drivers/spi/spi-atmel.c:1228:3: warning: format '%x' expects argument of type 'unsigned int', but argument 7 has type 'dma_addr_t' [-Wformat]
drivers/spi/spi-atmel.c:1228:3: warning: format '%x' expects argument of type 'unsigned int', but argument 9 has type 'dma_addr_t' [-Wformat]

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Mark Brown <broonie@linaro.org>