kernel - Do readonly check in .d_open method in mmcsd(4) and virtio_blk(4).
* Makes read-write open fail properly for read-only storage in mmcsd(4) and
virtio_blk(4), instead of only resulting in transfer errors for the
disk writes.
syscons - Add 16bit rendering code for UEFI and KMS driver framebuffers.
This fixes syscons rendering with KMS graphics drivers, when the driver
hands us a 16bit console framebuffer.
virtio_blk - Enable D_KVABIO API.
This should avoid some unnecessary page invalidations.
This driver already was compliant, since it never accesses any of the data
in the bio buffer.