plat/stm32: Implement fdt_read_uint32_default() as a wrapper

The STM32 platform code uses its own set of FDT helper functions,
although some of them are fairly generic.

Remove the implementation of fdt_read_uint32_default() and implement it
on top of the newly introduced fdt_read_uint32() function, then convert
all users over.

This also fixes two callers, which were slightly abusing the "default"
semantic.

Change-Id: I570533362b4846e58dd797a92347de3e0e5abb75
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
diff --git a/drivers/st/clk/stm32mp1_clk.c b/drivers/st/clk/stm32mp1_clk.c
index a16f36d..540c66a 100644
--- a/drivers/st/clk/stm32mp1_clk.c
+++ b/drivers/st/clk/stm32mp1_clk.c
@@ -1240,7 +1240,8 @@
 	uintptr_t clksrc_address = rcc_base + (clksrc >> 4);
 	unsigned long refclk;
 	uint32_t ifrge = 0U;
-	uint32_t src, value, fracv;
+	uint32_t src, value, fracv = 0;
+	void *fdt;
 
 	/* Check PLL output */
 	if (mmio_read_32(pllxcr) != RCC_PLLNCR_PLLON) {
@@ -1279,7 +1280,9 @@
 	}
 
 	/* Fractional configuration */
-	fracv = fdt_read_uint32_default(plloff, "frac", 0);
+	if (fdt_get_address(&fdt) == 1) {
+		fracv = fdt_read_uint32_default(fdt, plloff, "frac", 0);
+	}
 
 	value = fracv << RCC_PLLNFRACR_FRACV_SHIFT;
 	value |= RCC_PLLNFRACR_FRACLE;
@@ -1800,7 +1803,7 @@
 			continue;
 		}
 
-		fracv = fdt_read_uint32_default(plloff[i], "frac", 0);
+		fracv = fdt_read_uint32_default(fdt, plloff[i], "frac", 0);
 
 		ret = stm32mp1_pll_config(i, pllcfg[i], fracv);
 		if (ret != 0) {