drm/amdkfd: fix debug watchpoints for logical devices

The number of watchpoints should be set and constrained per logical
partition device, not by the socket device.

Signed-off-by: Jonathan Kim <jonathan.kim@amd.com>
Reviewed-by: Harish Kasiviswanathan <harish.kasiviswanathan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>