video, ipu: make ldb_clock configurable

make the ldb_clock configurable through the new define
CONFIG_SYS_LDB_CLOCK. This is needed as the ldb clock is not
always 650000000, for example on the aristainetos2 board,
where the ldb clock derives from PLL5 clock.
Signed-off-by: NHeiko Schocher <hs@denx.de>
Tested-by: NEric Nelson <eric.nelson@boundarydevices.com>

drivers/video/ipu_common.c

@@ -210,9 +210,13 @@ static struct clk ipu_clk = {
 	.usecount = 0,
 };
 
+#if !defined CONFIG_SYS_LDB_CLOCK
+#define CONFIG_SYS_LDB_CLOCK 65000000
+#endif
+
 static struct clk ldb_clk = {
 	.name = "ldb_clk",
-	.rate = 65000000,
+	.rate = CONFIG_SYS_LDB_CLOCK,
 	.usecount = 0,
 };