plat: imx7: refactor code for reuse

For the iMX7 SOCs, part of the code for platform
setup implementation can be reused and made
common for all these SoCs. This patch extracts
the common part for reuse.

Signed-off-by: Jun Nie <jun.nie@linaro.org>
Change-Id: I42fd4167e6903416df96a0159a046abf3896e878
diff --git a/plat/imx/common/include/imx_clock.h b/plat/imx/common/include/imx_clock.h
index ce245ad..d75dcff 100644
--- a/plat/imx/common/include/imx_clock.h
+++ b/plat/imx/common/include/imx_clock.h
@@ -1,6 +1,5 @@
 /*
- * Copyright (c) 2018, ARM Limited and Contributors. All rights reserved.
- *
+ * Copyright (c) 2018-2019, ARM Limited and Contributors. All rights reserved.
  * SPDX-License-Identifier: BSD-3-Clause
  */
 #ifndef IMX_CLOCK_H
@@ -819,6 +818,8 @@
 #define CCM_TRGT_MUX_WDOG_CLK_ROOT_USB_PLL			(BIT(26) | BIT(24))
 #define CCM_TRGT_MUX_WDOG_CLK_ROOT_REF_1M			(BIT(26) | BIT(25))
 #define CCM_TRGT_MUX_WDOG_CLK_ROOT_SYS_PLL_PFD1_DIV2		((BIT(26) | BIT(25) | BIT(24))
+#define WDOG_DEFAULT_CLK_SELECT					(CCM_TARGET_ROOT_ENABLE |\
+								CCM_TRGT_MUX_WDOG_CLK_ROOT_OSC_24M)
 
 /* Target CSI_MCLK_CLK_ROOT */