drm/amdgpu: add gc v9_4_3 rlc_funcs implementation

all the gc v9_4_3 registers fall in gc_rlcpdec address range
have different relative offsets and base_idx from the ones
defined in gc v9_0 ip headers. gc_v9_0_rlc_funcs can not be
reused anymore for gc v9_4_3

v2: drop unused handshake function (Alex)

Signed-off-by: Hawking Zhang <Hawking.Zhang@amd.com>
Reviewed-by: Le Ma <Le.Ma@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>