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/arch/powerpc/cpu/mpc83xx/ecc.c b/arch/powerpc/cpu/mpc83xx/ecc.c
index 68a7a78..7a8ec7f 100644
--- a/arch/powerpc/cpu/mpc83xx/ecc.c
+++ b/arch/powerpc/cpu/mpc83xx/ecc.c
@@ -138,7 +138,7 @@
 	}
 	if (argc == 3) {
 		if (strcmp(argv[1], "sbecnt") == 0) {
-			val = simple_strtoul(argv[2], NULL, 10);
+			val = dectoul(argv[2], NULL);
 			if (val > 255) {
 				printf("Incorrect Counter value, "
 				       "should be 0..255\n");
@@ -151,7 +151,7 @@
 			ddr->err_sbe = val;
 			return 0;
 		} else if (strcmp(argv[1], "sbethr") == 0) {
-			val = simple_strtoul(argv[2], NULL, 10);
+			val = dectoul(argv[2], NULL);
 			if (val > 255) {
 				printf("Incorrect Counter value, "
 				       "should be 0..255\n");