There were missing quotes for key "backspace" for scancodes.
This issue was found by github user @StagiaireAbritek
He opened an PR in github to fix it:
https://github.com/apache/nuttx/pull/15917
However he decided to abandon and close the PR, but because it is
an important fix I decided submit it upstream.
Signed-off-by: Alan C. Assis <acassis@gmail.com>