bindings: MAINTAINERS: fix references to Allwinner LRADC

The file got converted to yaml, but the reference at MAINTAINERS
was not updated.

Fixes: 5bf2845e ("dt-bindings: input: Convert Allwinner LRADC to a schema")
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>