MAINTAINERS: Remove the entry for the orphaned ams driver

I no longer have any hardware with the Apple motion sensor and thus
relinquish maintainership of the driver.

Remove the maintainers entry entirely, meaning the code will now fall
under "LINUX FOR POWER MACINTOSH".

Signed-off-by: Michael Hanselmann <linux-kernel@hansmi.ch>
[mpe: Drop the entry entirely, munge change log]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>