Suppress InputDevices validation logs

When the .kcm files are getting validated, there is logspam in the build
output, produced even when there aren't any errors. Add the "-q" option
to validate command to quiet these logs.

Test: $ rm -rf out/target/common/obj/ETC/validate_input_devices_keymaps_intermediates/
$ m. Note: just doing "m sync" or "m InputDevices" is not sufficient to
test this.
Bug: 35672363

Change-Id: Ib0213de7ee0fe965f1a202afdb718a2221017e06