amdgpu/pm: prevent array underflow in vega20_odn_edit_dpm_table()

In the Linux kernel, the following vulnerability has been resolved: amdgpu/pm: prevent array underflow in vega20_odn_edit_dpm_table() 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.