style: Fix "is is" typo across the codebase.

Correct duplicate "is is" word found in 181 files throughout the
codebase.
In most cases "is is" was changed to "is", but in contexts like
"MCU is is sleep mode" it was corrected to "MCU in sleep mode".

Also fixes a "the the" typo in net/inet/inet_sockif.c.

This is a pure style/documentation fix that improves code readability.

Signed-off-by: Huang Qi <huangqi3@xiaomi.com>

libs/libc/time/lib_localtime.c

@@ -1055,7 +1055,7 @@ static int tzload(FAR const char *name,
         }
     }
 
-  /* If type 0 is is unused in transitions, it's the type to use for early
+  /* If type 0 is unused in transitions, it's the type to use for early
    * times.
    */