amdgpu/pm: prevent array underflow in vega20_odn_edit_dpm_table()

amdgpu/pm: prevent array underflow in vega20_odn_edit_dpm_table()

[ Upstream commit 19b2c12f1d46f1a916c24203eb5a50502d4fbdd3 ]

In the PP_OD_EDIT_VDDC_CURVE case the "input_index" variable is capped at
2 but not checked for negative values so it results in an out of bounds
read.  This value comes from the user via sysfs.

Fixes: ae86668233a0 ("drm/amd/powerplay: added vega20 overdrive support V3")
Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>