drm/radeon/r7xx: fix copy paste typo in golden register setup

Uses the wrong array size for some asics which can lead
to garbage getting written to registers.

Fixes:
https://bugzilla.kernel.org/show_bug.cgi?id=60674

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org