Fix misc spelling errors found by lintian

Signed-off-by: Loïc Minier <loic.minier@linaro.org>
diff --git a/common/cmd_usb.c b/common/cmd_usb.c
index b5731a7..3ba6fff 100644
--- a/common/cmd_usb.c
+++ b/common/cmd_usb.c
@@ -588,7 +588,7 @@
 					break;
 			}
 			if (dev == NULL) {
-				printf("*** NO Device avaiable ***\n");
+				printf("*** No device available ***\n");
 				return 0;
 			} else {
 				usb_display_desc(dev);