drm/amdkfd: Use volatile MTYPE in default/alternate apertures

MTYPE_NC_NV (0) marks scalar/vector L1 cache lines as non-volatile.
Cache lines loaded through these apertures are intended to be
invalidated before (and sometimes during) a dispatch. The non-volatile
qualifier prevents these cache lines from being distinguished from
those loaded through the private aperture.

Use MTYPE_NC (1) instead on both Gfx7 and Gfx8. This allows the
compiler to use the BUFFER_WBINVL1_VOL instruction and is a precursor
to automatic per-dispatch scalar/vector L1 volatile invalidation.

Signed-off-by: Jay Cornwall <Jay.Cornwall@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>