drm/i915: Bump skl+ wm blocks to 11 bits

drm/i915: Bump skl+ wm blocks to 11 bits

On icl the plane watermark blocks field is 11 bits. Bump our define to
match so that readout won't ignore the extra bit. We can safely do this
for older platforms too since the unused bits are hardwired to zero.

Cc: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190205205056.30081-1-ville.syrjala@linux.intel.com
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>