nxp: Migrate CONFIG_DDR_CLK_FREQ to Kconfig

As this symbol can either be a fixed value or the function
get_board_ddr_clk, migration is tricky.  Introduce a choice of DYNAMIC
or STATIC_DDR_CLK_FREQ.  If DYNAMIC, we continue to use the board
defined get_board_ddr_clk function.  If STATIC, set CONFIG_DDR_CLK_FREQ
to that value and now include/clock_legacy.h contains the function
prototype or defines get_board_ddr_clk() to that static value.  Update
callers to test for DYNAMIC or STATIC.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/arch/arm/cpu/armv7/ls102xa/clock.c b/arch/arm/cpu/armv7/ls102xa/clock.c
index 940995e..984ae8b 100644
--- a/arch/arm/cpu/armv7/ls102xa/clock.c
+++ b/arch/arm/cpu/armv7/ls102xa/clock.c
@@ -42,8 +42,8 @@
 	unsigned long sysclk = CONFIG_SYS_CLK_FREQ;
 
 	sys_info->freq_systembus = sysclk;
-#ifdef CONFIG_DDR_CLK_FREQ
-	sys_info->freq_ddrbus = CONFIG_DDR_CLK_FREQ;
+#if defined(CONFIG_DYNAMIC_DDR_CLK_FREQ) || defined(CONFIG_STATIC_DDR_CLK_FREQ)
+	sys_info->freq_ddrbus = get_board_ddr_clk();
 #else
 	sys_info->freq_ddrbus = sysclk;
 #endif