macintosh/ams-input: Use true and false for boolean values

Assign true or false to boolean variables instead of an integer value.

This issue was detected with the help of Coccinelle

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Reviewed-by: Michael Hanselmann <public@hansmi.ch>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>