drm/amdgpu: use processed values for counting

adev->gfx.rlc has the values from rlc_hdr already processed by
le32_to_cpu.  Using the rlc_hdr values on big-endian machines causes
a kernel Oops due to writing well outside of the array (0x24000000
instead of 0x24).

Signed-off-by: A. Wilcox <AWilcox@Wilcox-Tech.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>