panfrost: Don't expose fp16 support on Bifrost unless explicitly requested

Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <!7636>
41 jobs for !7636 with bifrost-gles3 in 10 minutes and 58 seconds (queued for 9 seconds)
merge request