arm64: zynqmp: Fix command error values properly

Process errors from command via cmd_process_error() as is done on Versal.
When internal function returns different number then CMD_RET_SUCCESS(0),
CMD_RET_FAILURE(1) or CMD_RET_USAGE(-1) shell react on these errors by
throwing an error like
"exit not allowed from main input shell." that's why use
cmd_process_error() to make sure that error code is all the time correct.

Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/d511935ba10daf95c70996fae6e6ffc374efffa0.1685618464.git.michal.simek@amd.com
diff --git a/board/xilinx/zynqmp/cmds.c b/board/xilinx/zynqmp/cmds.c
index c1224bd..9d375b0 100644
--- a/board/xilinx/zynqmp/cmds.c
+++ b/board/xilinx/zynqmp/cmds.c
@@ -394,17 +394,17 @@
 		     char *const argv[])
 {
 	struct cmd_tbl *c;
+	int ret = CMD_RET_USAGE;
 
 	if (argc < 2)
 		return CMD_RET_USAGE;
 
 	c = find_cmd_tbl(argv[1], &cmd_zynqmp_sub[0],
 			 ARRAY_SIZE(cmd_zynqmp_sub));
-
 	if (c)
-		return c->cmd(c, flag, argc, argv);
-	else
-		return CMD_RET_USAGE;
+		ret = c->cmd(c, flag, argc, argv);
+
+	return cmd_process_error(c, ret);
 }
 
 /***************************************************/