Remove Kingfisher btwilink disabling

Remove Kingfisher btwilink disabling

Remove DEMO_ENABLE_BTWILINK hook and associated conf file recipe used
to make using the btwilink driver an explicit opt-in, as the driver
has been removed from the meta-rcar Kingfisher BSP layer in its new
scarthgap-v5.9.4 branch in favor of the mainline kernel driver.
Since the Kingfisher is not a primary demo platform at this point,
leaving it to default to its onboard Bluetooth support seems
reasonable versus trying to update this scheme.

Bug-AGL: SPEC-5191, SPEC-5214

Change-Id: Iece5d2671ab36f4191d950bfa50e320f35dbef3b
Signed-off-by: Scott Murray <scott.murray@konsulko.com>
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/meta-agl-demo/+/30249
ci-image-boot-test: Jenkins Job builder account
ci-image-build: Jenkins Job builder account
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>
Tested-by: Jenkins Job builder account