scripts: dt_to_config: fix grammar and a typo in --help text

- grammar: singular/plural inconsistency
- typo: "of" -> "or"

Signed-off-by: Markus Heidelberg <[e-mail]>
Signed-off-by: Rob Herring (Arm) <[e-mail]>

scripts/dtc/dt_to_config

···
     "compatible is white listed",
     "matching driver and/or kernel config is hard coded",
     "kernel config hard coded in Makefile",
-    "one or more kernel config file options is not set",
-    "one or more kernel config file options is set to 'm'",
-    "one or more kernel config file options is set to 'y'",
-    "one of more kernel config file options fails to have correct value"
+    "one or more kernel config file options are not set",
+    "one or more kernel config file options are set to 'm'",
+    "one or more kernel config file options are set to 'y'",
+    "one or more kernel config file options fail to have correct value"
 );