The code managing the dbuf slices is borked and needs some
real work to fix. In the meantime let's just stop using the
second slice.

v2: Drop the change to intel_enabled_dbuf_slices_num() (Mahesh)

Cc: Mahesh Kumar <mahesh1.sh.kumar@gmail.com>
Reviewed-by: Imre Deak <imre.deak@intel.com> #v1
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190130155110.12918-1-ville.syrjala@linux.intel.comReviewed-by: NMahesh Kumar <mahesh1.sh.kumar@gmail.com>