global: Convert simple_strtoul() with decimal to dectoul()

It is a pain to have to specify the value 10 in each call. Add a new
dectoul() function and update the code to use it.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/board/sifive/unmatched/hifive-platform-i2c-eeprom.c b/board/sifive/unmatched/hifive-platform-i2c-eeprom.c
index b230a71..2b985b9 100644
--- a/board/sifive/unmatched/hifive-platform-i2c-eeprom.c
+++ b/board/sifive/unmatched/hifive-platform-i2c-eeprom.c
@@ -324,7 +324,7 @@
 {
 	unsigned long p;
 
-	p = simple_strtoul(string, &string, 10);
+	p = dectoul(string, &string);
 	if (p > U8_MAX) {
 		printf("%s must not be greater than %d\n", "PCB revision",
 		       U8_MAX);
@@ -366,7 +366,7 @@
 {
 	unsigned long p;
 
-	p = simple_strtoul(string, &string, 10);
+	p = dectoul(string, &string);
 	if (p > U8_MAX) {
 		printf("%s must not be greater than %d\n", "BOM variant",
 		       U8_MAX);
@@ -389,7 +389,7 @@
 {
 	unsigned long p;
 
-	p = simple_strtoul(string, &string, 10);
+	p = dectoul(string, &string);
 	if (p > U16_MAX) {
 		printf("%s must not be greater than %d\n", "Product ID",
 		       U16_MAX);