fuzz/mime: fix call conditions and args

The SMTP parser should not supply lines w/o EOL chars to the mime
parser unless its in the BODY parsing stage. Mimic this in the fuzz
target by testing the state for inputs that have no EOL.

Additionally, make sure the delim cnt reflects the missing EOL.

src/tests/fuzz/fuzz_mimedecparseline.c

@@ -43,7 +43,8 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
     while (1) {
         uint8_t * next = memchr(buffer, '\n', size);
         if (next == NULL) {
-            (void) MimeDecParseLine(buffer, size, 1, state);
+            if (state->state_flag >= BODY_STARTED)
+                (void)MimeDecParseLine(buffer, size, 0, state);
             break;
         } else {
             (void) MimeDecParseLine(buffer, next - buffer, 1, state);