drm/amd/display: fix bug where we are creating bogus i2c aux

[WHY]
we were using  6 instances based on i2caux_dce110.c

[HOW]
pass in how many instances to ctor

Signed-off-by: Tony Cheng <tony.cheng@amd.com>
Reviewed-by: Yongqiang Sun <yongqiang.sun@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>