Update Xbox BT controller mapping for new FW

The Xbox controller (product id 0x02fd) is going to have a new firmware
update this fall that sends a different keycode (316/BUTTON_MODE) for
the Xbox button.  The goal is to enable the Xbox button to make it to
apps on all Android versions -- with our without a controller-specific
key mapping file.

Unfortunately, the new Vendor_045e_Product_02fd.kl key mapping file
that was added to Android Q maps the pre-firmware-update
Xbox key code (172) to BUTTON_MODE, yet it makes no mention of key 316.
This results in apps getting a raw 316 scan code instead of
a BUTTON_MODE KeyEvent when using a controller with the latest firmware
on Android Q.

The fix is to add an additional key mapping for 316 that *also* maps to
BUTTON_MODE.  With both mappings in place, both pre and post
firmware-updated controllers will get the correct behavior for the
Xbox button on Android Q.

Test: AFAIK, no CTS tests exist for Xbox controller key mappings;
we'll need to add some at a later date.  I was unable to test this
change because I'm unable to write to the system directory on any
of my devices, but I know that mapping 316 to BUTTON_MODE will
fix the issue.

Signed-off-by: Jared Henderson <jaredh.microsoft@gmail.com>

Bug: 139512030
Bug: 140808513

Merged-In: I8600ea79a0aa8557267d6ca712e5d56680e7a98b
Change-Id: I8600ea79a0aa8557267d6ca712e5d56680e7a98b