cmd: fdt: Fix fdt rsvmem behavior on non-existent index and error message space

In case 'fdt rsvmem delete index' is passed a non-existent index, one
which does not exist in 'fdt rsvmem print', then the following command
triggers a print of help message for 'fdt' command instead of erroring
out:
=> fdt rsvmem delete 1234
This is because the subcommand errornously returns 'err' instead of
CMD_RET_FAILURE, fix it. Furthermore, align the number of spaces past
fdt_del_mem_rsv() and fdt_add_mem_rsv() in error message with the rest
of the code.

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/cmd/fdt.c b/cmd/fdt.c
index 644b58a..29d7488 100644
--- a/cmd/fdt.c
+++ b/cmd/fdt.c
@@ -644,18 +644,18 @@
 			err = fdt_add_mem_rsv(working_fdt, addr, size);
 
 			if (err < 0) {
-				printf("libfdt fdt_add_mem_rsv():  %s\n",
+				printf("libfdt fdt_add_mem_rsv(): %s\n",
 					fdt_strerror(err));
-				return err;
+				return CMD_RET_FAILURE;
 			}
 		} else if (argv[2][0] == 'd') {
 			unsigned long idx = hextoul(argv[3], NULL);
 			int err = fdt_del_mem_rsv(working_fdt, idx);
 
 			if (err < 0) {
-				printf("libfdt fdt_del_mem_rsv():  %s\n",
+				printf("libfdt fdt_del_mem_rsv(): %s\n",
 					fdt_strerror(err));
-				return err;
+				return CMD_RET_FAILURE;
 			}
 		} else {
 			/* Unrecognized command */