ARM: EXYNOS: Add apb_pclk clkdev entry for mdma1

Amba core assumes the pclk to be named as apb_pclk. During device probe,
it tries to get that clock and enable that. When PM_RUNTIME is enabled,
dma clock is not explicitly enabled in pl330_probe, which causes device
probe to fail. Adding a clkdev entry for apb_pclk for mdma1 fixes the
problem.

This patch fixes following runtime error.

dma-pl330 dma-pl330.2: PERIPH_ID 0x0, PCELL_ID 0x0 !
dma-pl330: probe of dma-pl330.2 failed with error -22

Signed-off-by: Tushar Behera <tushar.behera@linaro.org>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>