common: nvedit: use snprintf instead of sprintf

Use snprintf to replace sprintf.

Coverity log:
"
Unbounded source buffer (STRING_SIZE)
string_size: Passing string init_val of unknown size to sprintf.
"

Reported-by: Coverity
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Cc: Tom Rini <trini@konsulko.com>
Cc: Simon Glass <sjg@chromium.org>
Reviewed-by: Joe Hershberger <joe.hershberger@ni.com>
diff --git a/common/cmd_nvedit.c b/common/cmd_nvedit.c
index 2f9cdd0..5ae9d9d 100644
--- a/common/cmd_nvedit.c
+++ b/common/cmd_nvedit.c
@@ -595,7 +595,7 @@
 	/* Set read buffer to initial value or empty sting */
 	init_val = getenv(argv[1]);
 	if (init_val)
-		sprintf(buffer, "%s", init_val);
+		snprintf(buffer, CONFIG_SYS_CBSIZE, "%s", init_val);
 	else
 		buffer[0] = '\0';